Added a file that defines a new generic image interface for images in dlib.

This is the dlib/image_processing/generic_image.h file.  Then I changed all the
image processing functions so that they use this interface.  All the changes
are very minor, but there are just a lot of them.

Any user code that was using array2d objects to represent images will still
work.  However, this change makes it so that users can use their own custom
image objects with dlib by simply implementing a few global functions for their
image object.

dlib/array2d.h

@@ -6,6 +6,7 @@
 
 #include "array2d/array2d_kernel.h"
 #include "array2d/serialize_pixel_overloads.h"
+#include "array2d/array2d_generic_image.h"
 
 #endif // DLIB_ARRAY2d_
 

dlib/array2d/array2d_generic_image.h

+// Copyright (C) 2014  Davis E. King (davis@dlib.net)
+// License: Boost Software License   See LICENSE.txt for the full license.
+#ifndef DLIB_ARRAY2D_GENERIC_iMAGE_H__
+#define DLIB_ARRAY2D_GENERIC_iMAGE_H__
+
+#include "array2d_kernel.h"
+#include "../image_processing/generic_image.h"
+
+namespace dlib
+{
+    template <typename T, typename mm>
+    struct image_traits<array2d<T,mm> >
+    {
+        typedef T pixel_type;
+    };
+
+    template <typename T, typename mm>
+    inline long num_rows( const array2d<T,mm>& img) { return img.nr(); }
+    template <typename T, typename mm>
+    inline long num_columns( const array2d<T,mm>& img) { return img.nc(); }
+
+    template <typename T, typename mm>
+    inline void set_image_size(
+        array2d<T,mm>& img,
+        long rows,
+        long cols 
+    ) { img.set_size(rows,cols); }
+
+    template <typename T, typename mm>
+    inline void* image_data(
+        array2d<T,mm>& img
+    )
+    {
+        if (img.size() != 0)
+            return &img[0][0];
+        else
+            return 0;
+    }
+
+    template <typename T, typename mm>
+    inline const void* image_data(
+        const array2d<T,mm>& img
+    )
+    {
+        if (img.size() != 0)
+            return &img[0][0];
+        else
+            return 0;
+    }
+
+    template <typename T, typename mm>
+    inline long width_step(
+        const array2d<T,mm>& img
+    ) 
+    { 
+        return img.width_step(); 
+    }
+
+}
+
+#endif // DLIB_ARRAY2D_GENERIC_iMAGE_H__
+

dlib/geometry/rectangle.h

@@ -9,6 +9,7 @@
 #include <iostream>
 #include "../serialize.h"
 #include "vector.h"
+#include "../image_processing/generic_image.h"
 
 namespace dlib
 {
@@ -645,7 +646,7 @@ namespace dlib
         const T& m
     )
     {
-        return rectangle(0, 0, m.nc()-1, m.nr()-1);
+        return rectangle(0, 0, num_columns(m)-1, num_rows(m)-1);
     }
 
 // ----------------------------------------------------------------------------------------

dlib/geometry/rectangle_abstract.h

@@ -715,9 +715,12 @@ namespace dlib
     );
     /*!
         requires
-            - T has nr() and nc() functions that return longs
+            - It must be possible to determine the number of "rows" and "columns" in m.
+              Either by calling num_rows(m) and num_columns(m) or by calling m.nr() and
+              m.nc() to obtain the number of rows and columns respectively.  Moreover,
+              these routines should return longs.
         ensures
-            - returns rectangle(0, 0, m.nc()-1, m.nr()-1)
+            - returns rectangle(0, 0, num_columns(m)-1, num_rows(m)-1)
               (i.e. assuming T represents some kind of rectangular grid, such as
               the dlib::matrix or dlib::array2d objects, this function returns the
               bounding rectangle for that gridded object.)

dlib/gui_widgets/widgets.h

@@ -3253,12 +3253,12 @@ namespace dlib
 
             // if the new image has a different size when compared to the previous image
             // then we should readjust the total rectangle size.
-            if (new_img.nr() != img.nr() || new_img.nc() != img.nc())
+            if (num_rows(new_img) != img.nr() || num_columns(new_img) != img.nc())
             {
                 if (zoom_in_scale != 1)
-                    set_total_rect_size(new_img.nc()*zoom_in_scale, new_img.nr()*zoom_in_scale);
+                    set_total_rect_size(num_columns(new_img)*zoom_in_scale, num_rows(new_img)*zoom_in_scale);
                 else
-                    set_total_rect_size(new_img.nc()/zoom_out_scale, new_img.nr()/zoom_out_scale);
+                    set_total_rect_size(num_columns(new_img)/zoom_out_scale, num_rows(new_img)/zoom_out_scale);
             }
             else
             {

dlib/image_keypoint/fine_hog_image.h

@@ -66,7 +66,7 @@ namespace dlib
             const image_type& img
         )
         {
-            COMPILE_TIME_ASSERT( pixel_traits<typename image_type::type>::has_alpha == false );
+            COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<image_type>::pixel_type>::has_alpha == false );
             load_impl(mat(img));
         }
 

dlib/image_keypoint/fine_hog_image_abstract.h

@@ -103,7 +103,7 @@ namespace dlib
             requires
                 - image_type is a dlib::matrix or something convertible to a matrix
                   via mat()
-                - pixel_traits<typename image_type::type>::has_alpha == false
+                - pixel_traits<typename image_traits<image_type>::pixel_type>::has_alpha == false
             ensures
                 - if (img.nr() < min_size || img.nc() < min_size) then
                     - the image is too small so we don't compute anything on it

dlib/image_keypoint/hashed_feature_image.h

@@ -309,7 +309,7 @@ namespace dlib
             // use the inverse frequency as the scale for each feature.  We also scale
             // these counts so that they are invariant to the size of the image (we scale
             // them so they all look like they come from a 500x400 images).
-            const double scale = img.size()/(500.0*400.0);
+            const double scale = image_size(img)/(500.0*400.0);
             for (unsigned long i = 0; i < feat_counts.size(); ++i)
             {
                 feat_counts[i] = scale/feat_counts[i];

dlib/image_keypoint/hog.h

@@ -82,7 +82,7 @@ namespace dlib
             const image_type& img
         )
         {
-            COMPILE_TIME_ASSERT( pixel_traits<typename image_type::type>::has_alpha == false );
+            COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<image_type>::pixel_type>::has_alpha == false );
             load_impl(mat(img));
         }
 

dlib/image_keypoint/hog_abstract.h

@@ -158,8 +158,8 @@ namespace dlib
         /*!
             requires
                 - image_type is a dlib::matrix or something convertible to a matrix
-                  via mat()
-                - pixel_traits<typename image_type::type>::has_alpha == false
+                  via mat().
+                - pixel_traits<typename image_traits<image_type>::pixel_type>::has_alpha == false
             ensures
                 - if (img.nr() < min_size || img.nc() < min_size) then
                     - the image is too small so we don't compute anything on it

dlib/image_keypoint/poly_image.h

@@ -138,7 +138,7 @@ namespace dlib
             const image_type& img
         )
         {
-            COMPILE_TIME_ASSERT( pixel_traits<typename image_type::type>::has_alpha == false );
+            COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<image_type>::pixel_type>::has_alpha == false );
 
             poly_coef.resize(get_num_dimensions());
             des.set_size(get_num_dimensions());

dlib/image_keypoint/poly_image_abstract.h

@@ -166,8 +166,9 @@ namespace dlib
         );
         /*!
             requires
-                - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-                - pixel_traits<typename image_type::type>::has_alpha == false
+                - image_type == an image object that implements the interface defined in
+                  dlib/image_processing/generic_image.h 
+                - pixel_traits<typename image_traits<image_type>::pixel_type>::has_alpha == false
             ensures
                 - Performs the feature extraction described in the WHAT THIS OBJECT REPRESENTS
                   section above.  This means after load() finishes you can call (*this)(row,col) 

dlib/image_keypoint/surf.h

@@ -248,7 +248,7 @@ namespace dlib
         );
 
         // Figure out the proper scalar type we should use to work with these pixels.  
-        typedef typename pixel_traits<typename image_type::type>::basic_pixel_type bp_type;
+        typedef typename pixel_traits<typename image_traits<image_type>::pixel_type>::basic_pixel_type bp_type;
         typedef typename promote<bp_type>::type working_pixel_type;
 
         // make an integral image first

dlib/image_keypoint/surf_abstract.h

@@ -133,8 +133,10 @@ namespace dlib
         requires
             - max_points > 0
             - detection_threshold >= 0
-            - image_type == a type that implements the array2d/array2d_kernel_abstract.h interface
-            - pixel_traits<image_type::type> must be defined
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - Let P denote the type of pixel in img, then we require:
+                - pixel_traits<P>::has_alpha == false 
         ensures
             - This function runs the complete SURF algorithm on the given input image and 
               returns the points it found. 

dlib/image_loader/image_loader.h

@@ -31,10 +31,11 @@ namespace dlib
         typename image_type 
         >
     void load_bmp (
-        image_type& image,
+        image_type& image_,
         std::istream& in_
     )
     {
+        image_view<image_type> image(image_);
         try
         {
             unsigned long bytes_read_so_far = 0;
@@ -550,10 +551,11 @@ namespace dlib
         typename image_type 
         >
     void load_dng (
-        image_type& image,
+        image_type& image_,
         std::istream& in
     )
     {
+        image_view<image_type> image(image_);
         using namespace dng_helpers_namespace;
         try
         {
@@ -788,7 +790,7 @@ namespace dlib
                         
                         // Only use long double precision if the target image contains long
                         // doubles because it's slower to use those.
-                        if (!is_same_type<typename image_type::type,long double>::value)
+                        if (!is_same_type<typename image_traits<image_type>::pixel_type,long double>::value)
                         {
                             double temp = cur;
                             assign_pixel(image[r][c],temp);

dlib/image_loader/image_loader_abstract.h

@@ -29,8 +29,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type::type> is defined  
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
         ensures
             - #image == the image of the MS Windows BMP file that was available 
               in the input stream in.  
@@ -61,8 +61,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type::type> is defined  
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
         ensures
             - opens the file indicated by file_name with an input file stream named fin 
               and performs:
@@ -87,8 +87,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type::type> is defined  
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
         ensures
             - #image == the image of the dlib dng file that was available 
               in the input stream in. 
@@ -119,8 +119,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type::type> is defined  
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
         ensures
             - opens the file indicated by file_name with an input file stream named fin 
               and performs:

dlib/image_loader/jpeg_loader.h

@@ -25,7 +25,7 @@ namespace dlib
         bool is_rgb() const;
 
         template<typename T>
-        void get_image( T& t) const
+        void get_image( T& t_) const
         {
 #ifndef DLIB_JPEG_SUPPORT
             /* !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
@@ -36,6 +36,7 @@ namespace dlib
             !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*/
             COMPILE_TIME_ASSERT(sizeof(T) == 0);
 #endif
+            image_view<T> t(t_);
 
             t.set_size( height_, width_ );
             for ( unsigned n = 0; n < height_;n++ )

dlib/image_loader/jpeg_loader_abstract.h

@@ -99,8 +99,8 @@ namespace dlib
         ) const;
         /*!
             requires
-                - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-                - pixel_traits<typename image_type::type> is defined  
+                - image_type == an image object that implements the interface defined in
+                  dlib/image_processing/generic_image.h 
             ensures
                 - loads the JPEG image stored in this object into img
         !*/
@@ -118,8 +118,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type::type> is defined  
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
         ensures
             - performs: jpeg_loader(file_name).get_image(image);
     !*/

dlib/image_loader/load_image_abstract.h

@@ -15,8 +15,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type::type> is defined  
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
         ensures
             - let EXT == the extension of the file given by file_name converted
               to lower case (i.e.  the part of the file after the '.')

dlib/image_loader/png_loader.h

@@ -30,7 +30,7 @@ namespace dlib
         unsigned int bit_depth () const { return bit_depth_; }
 
         template<typename T>
-        void get_image( T& t) const
+        void get_image( T& t_) const
         {
 #ifndef DLIB_PNG_SUPPORT
             /* !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
@@ -42,7 +42,8 @@ namespace dlib
             COMPILE_TIME_ASSERT(sizeof(T) == 0);
 #endif
 
-            typedef typename T::type pixel_type;
+            typedef typename image_traits<T>::pixel_type pixel_type;
+            image_view<T> t(t_);
             t.set_size( height_, width_ );
 
 
@@ -148,7 +149,7 @@ namespace dlib
             }
             else if (is_rgba() && bit_depth_ == 8)
             {
-                if (!pixel_traits<typename T::type>::has_alpha)
+                if (!pixel_traits<pixel_type>::has_alpha)
                     assign_all_pixels(t,0);
 
                 for ( unsigned n = 0; n < height_;n++ )
@@ -167,7 +168,7 @@ namespace dlib
             }
             else if (is_rgba() && bit_depth_ == 16)
             {
-                if (!pixel_traits<typename T::type>::has_alpha)
+                if (!pixel_traits<pixel_type>::has_alpha)
                     assign_all_pixels(t,0);
 
                 for ( unsigned n = 0; n < height_;n++ )

dlib/image_loader/png_loader_abstract.h

@@ -127,8 +127,8 @@ namespace dlib
         ) const;
         /*!
             requires
-                - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-                - pixel_traits<typename image_type::type> is defined  
+                - image_type == an image object that implements the interface defined in
+                  dlib/image_processing/generic_image.h 
             ensures
                 - loads the PNG image stored in this object into img
         !*/
@@ -146,8 +146,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type::type> is defined  
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
         ensures
             - performs: png_loader(file_name).get_image(image);
     !*/

dlib/image_processing/generic_image.h

+// Copyright (C) 2014  Davis E. King (davis@dlib.net)
+// License: Boost Software License   See LICENSE.txt for the full license.
+#ifndef DLIB_GeNERIC_IMAGE_H__
+#define DLIB_GeNERIC_IMAGE_H__
+
+namespace dlib
+{
+
+    /*!
+        In dlib, an "image" is any object that implements the generic image interface.  In
+        particular, this simply means that an image type (let's refer to it as image_type
+        from here on) implements the following seven global functions:
+            - long        num_rows      (const image_type& img)
+            - long        num_columns   (const image_type& img)
+            - void        set_image_size(      image_type& img, long rows, long cols)
+            - void*       image_data    (      image_type& img)
+            - const void* image_data    (const image_type& img)
+            - long        width_step    (const image_type& img)
+            - void        swap          (      image_type& a, image_type& b)
+        And also provides a specialization of the image_traits template that looks like:
+            namespace dlib
+            {
+                template <> 
+                struct image_traits<image_type>
+                {
+                    typedef the_type_of_pixel_used_in_image_type pixel_type;
+                };
+            }
+
+        Additionally, an image object must be default constructable.  This means that 
+        expressions of the form:
+            image_type img;
+        Must be legal.
+
+        Finally, the type of pixel in image_type must have a pixel_traits specialization.
+        That is, pixel_traits<typename image_traits<image_type>::pixel_type> must be one of
+        the specializations of pixel_traits.  
+        
+        
+        To be very precise, the seven functions defined above are defined thusly:
+
+            long num_rows(
+                const image_type& img
+            ); 
+            /!*
+                ensures
+                    - returns the number of rows in the given image
+            *!/
+
+            long num_columns(
+                const image_type& img
+            );
+            /!*
+                ensures
+                    - returns the number of columns in the given image
+            *!/
+
+            void set_image_size(
+                image_type& img,
+                long rows,
+                long cols 
+            );
+            /!*
+                requires
+                    - rows >= 0 && cols >= 0
+                ensures
+                    - num_rows(#img) == rows
+                    - num_columns(#img) == cols
+            *!/
+
+            void* image_data(
+                image_type& img
+            );
+            /!*
+                ensures
+                    - returns a non-const pointer to the pixel at row and column position 0,0
+                      in the given image.  Or if the image has zero rows or columns in it
+                      then this function returns NULL.
+                    - The image lays pixels down in row major order.  However, there might
+                      be padding at the end of each row.  The amount of padding is given by
+                      width_step(img).
+            *!/
+
+            const void* image_data(
+                const image_type& img
+            );
+            /!*
+                ensures
+                    - returns a const pointer to the pixel at row and column position 0,0 in
+                      the given image.  Or if the image has zero rows or columns in it then
+                      this function returns NULL.
+                    - The image lays pixels down in row major order.  However, there might
+                      be padding at the end of each row.  The amount of padding is given by
+                      width_step(img).
+            *!/
+
+            long width_step(
+                const image_type& img
+            );
+            /!*
+                ensures
+                    - returns the size of one row of the image, in bytes.  More precisely,
+                      return a number N such that: (char*)image_data(img) + N*R == a
+                      pointer to the first pixel in the R-th row of the image. This means
+                      that the image must lay its pixels down in row major order.
+            *!/
+
+            void swap(
+                image_type& a,
+                image_type& b
+            );
+            /!*
+                ensures
+                    - swaps the state of a and b
+            *!/
+    !*/
+
+// ----------------------------------------------------------------------------------------
+
+    template <typename image_type>
+    struct image_traits;
+    /*!
+        WHAT THIS OBJECT REPRESENTS
+            This is a traits class for generic image objects.  You can use it to find out
+            the pixel type contained within an image via an expression of the form:
+                image_traits<image_type>::pixel_type
+    !*/
+
+// ----------------------------------------------------------------------------------------
+// ----------------------------------------------------------------------------------------
+//                   UTILITIES TO MAKE ACCESSING IMAGE PIXELS SIMPLER
+// ----------------------------------------------------------------------------------------
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename image_type
+        >
+    class image_view
+    {
+        /*!
+            REQUIREMENTS ON image_type
+                image_type must be an image object as defined at the top of this file.  
+
+            WHAT THIS OBJECT REPRESENTS
+                This object takes an image object and wraps it with an interface that makes
+                it look like a dlib::array2d.  That is, it makes it look similar to a
+                regular 2-dimensional C style array, making code which operates on the
+                pixels simple to read.
+
+                Note that an image_view instance is valid until the image given to its
+                constructor is modified through an interface other than the image_view
+                instance.  This is because, for example, someone might cause the underlying
+                image object to reallocate its memory, thus invalidating the pointer to its
+                pixel data stored in the image_view.    
+
+                As an side, there reason why this object stores a pointer to the image
+                object's data and uses that pointer instead of calling image_data() each
+                time a pixel is accessed is to allow for image objects to implement
+                complex, and possibly slow, image_data() functions.  For example, an image
+                object might perform some kind of synchronization between a GPU and the
+                host memory during a call to image_data().  Therefore, we call image_data()
+                only in image_view's constructor to avoid the performance penalty of
+                calling it for each pixel access.
+        !*/
+
+    public:
+        typedef typename image_traits<image_type>::pixel_type pixel_type;
+
+        image_view(
+            image_type& img
+        ) : 
+            _data((char*)image_data(img)), 
+            _width_step(width_step(img)),
+            _nr(num_rows(img)),
+            _nc(num_columns(img)),
+            _img(&img) 
+        {}
+
+        long nr() const { return _nr; }
+        /*!
+            ensures
+                - returns the number of rows in this image.
+        !*/
+
+        long nc() const { return _nc; }
+        /*!
+            ensures
+                - returns the number of columns in this image.
+        !*/
+
+        unsigned long size() const { return static_cast<unsigned long>(nr()*nc()); }
+        /*!
+            ensures
+                - returns the number of pixels in this image.
+        !*/
+
+        pixel_type* operator[] (long row) { return (pixel_type*)(_data+_width_step*row); }
+        /*!
+            requires
+                - 0 <= row < nr()
+            ensures
+                - returns a pointer to the first pixel in the row-th row.  Therefore, the
+                  pixel at row and column position r,c can be accessed via (*this)[r][c].
+        !*/
+
+        const pixel_type* operator[] (long row) const { return (const pixel_type*)(_data+_width_step*row); }
+        /*!
+            requires
+                - 0 <= row < nr()
+            ensures
+                - returns a const pointer to the first pixel in the row-th row.  Therefore,
+                  the pixel at row and column position r,c can be accessed via
+                  (*this)[r][c].
+        !*/
+
+        void set_size(long rows, long cols) { set_image_size(*_img, rows, cols); *this = *_img; }
+        /*!
+            requires
+                - rows >= 0 && cols >= 0
+            ensures
+                - Tells the underlying image to resize itself to have the given number of
+                  rows and columns.
+                - #nr() == rows
+                - #nc() == cols
+        !*/
+
+        void clear() { set_size(0,0); }
+        /*!
+            ensures
+                - sets the image to have 0 pixels in it.
+        !*/
+
+    private:
+
+        char* _data;
+        long _width_step;
+        long _nr;
+        long _nc;
+        image_type* _img;
+    };
+
+// ----------------------------------------------------------------------------------------
+
+    template <typename image_type>
+    class const_image_view
+    {
+        /*!
+            REQUIREMENTS ON image_type
+                image_type must be an image object as defined at the top of this file.  
+
+            WHAT THIS OBJECT REPRESENTS
+                This object is just like the image_view except that it provides a "const"
+                view into an image.  That is, it has the same interface as image_view
+                except that you can't modify the image through a const_image_view.
+        !*/
+
+    public:
+        typedef typename image_traits<image_type>::pixel_type pixel_type;
+
+        const_image_view(
+            const image_type& img
+        ) : 
+            _data((char*)image_data(img)), 
+            _width_step(width_step(img)),
+            _nr(num_rows(img)),
+            _nc(num_columns(img))
+        {}
+
+        long nr() const { return _nr; }
+        long nc() const { return _nc; }
+        unsigned long size() const { return static_cast<unsigned long>(nr()*nc()); }
+        const pixel_type* operator[] (long row) const { return (const pixel_type*)(_data+_width_step*row); }
+
+    private:
+        const char* _data;
+        long _width_step;
+        long _nr;
+        long _nc;
+    };
+
+// ----------------------------------------------------------------------------------------
+
+    template <typename image_type>
+    image_view<image_type> make_image_view ( image_type& img) 
+    { return image_view<image_type>(img); }
+    /*!
+        requires
+            - image_type == an image object that implements the interface defined at the
+              top of this file.
+        ensures
+            - constructs an image_view from an image object
+    !*/
+
+    template <typename image_type>
+    const_image_view<image_type> make_image_view (const image_type& img) 
+    { return const_image_view<image_type>(img); }
+    /*!
+        requires
+            - image_type == an image object that implements the interface defined at the
+              top of this file.
+        ensures
+            - constructs a const_image_view from an image object
+    !*/
+
+// ----------------------------------------------------------------------------------------
+
+    template <typename image_type>
+    inline unsigned long image_size(
+        const image_type& img
+    ) { return num_columns(img)*num_rows(img); }
+    /*!
+        requires
+            - image_type == an image object that implements the interface defined at the
+              top of this file.
+        ensures
+            - returns the number of pixels in the given image.
+    !*/
+
+// ----------------------------------------------------------------------------------------
+
+    template <typename image_type>
+    inline long num_rows(
+        const image_type& img
+    ) { return img.nr(); }
+    /*!
+        ensures
+            - By default, try to use the member function .nr() to determine the number
+              of rows in an image.  However, as stated at the top of this file, image
+              objects should provide their own overload of num_rows() if needed.
+    !*/
+
+    template <typename image_type>
+    inline long num_columns(
+        const image_type& img
+    ) { return img.nc(); }
+    /*!
+        ensures
+            - By default, try to use the member function .nc() to determine the number
+              of columns in an image.  However, as stated at the top of this file, image
+              objects should provide their own overload of num_rows() if needed.
+    !*/
+
+// ----------------------------------------------------------------------------------------
+
+}
+
+#endif // DLIB_GeNERIC_IMAGE_H__
+

dlib/image_processing/scan_fhog_pyramid.h

@@ -589,8 +589,6 @@ namespace dlib
             feats.set_size(levels);
 
 
-            typedef typename image_type::type pixel_type;
-            typedef typename image_type::mem_manager_type mem_manager_type;
 
             // build our feature pyramid
             fe(img, feats[0], cell_size,filter_rows_padding,filter_cols_padding);
@@ -600,7 +598,7 @@ namespace dlib
 
             if (feats.size() > 1)
             {
-                array2d<pixel_type,mem_manager_type> temp1, temp2;
+                image_type temp1, temp2;
                 pyr(img, temp1);
                 fe(temp1, feats[1], cell_size,filter_rows_padding,filter_cols_padding);
                 swap(temp1,temp2);

dlib/image_processing/scan_image.h

@@ -56,8 +56,8 @@ namespace dlib
 
         for (unsigned long i = 0; i < images.size(); ++i)
         {
-            if (images[0].nr() != images[i].nr() ||
-                images[0].nc() != images[i].nc())
+            if (num_rows(images[0]) != num_rows(images[i]) ||
+                num_columns(images[0]) != num_columns(images[i]))
                 return false;
         }
 
@@ -93,7 +93,7 @@ namespace dlib
 #endif
 
 
-        typedef typename image_array_type::type::type pixel_type;
+        typedef typename image_traits<typename image_array_type::type>::pixel_type pixel_type;
         typedef typename promote<pixel_type>::type ptype;
 
         ptype temp = 0;
@@ -151,7 +151,7 @@ namespace dlib
             );
         }
 #endif
-        typedef typename image_array_type::type::type pixel_type;
+        typedef typename image_traits<typename image_array_type::type>::pixel_type pixel_type;
         typedef typename promote<pixel_type>::type ptype;
 
         ptype temp = 0;
@@ -190,12 +190,13 @@ namespace dlib
         >
     void find_points_above_thresh (
         std::vector<std::pair<double, point> >& dets,
-        const image_type& img,
+        const image_type& img_,
         const double thresh,
         const unsigned long max_dets
     )
     {
-        typedef typename image_type::type ptype;
+        const_image_view<image_type> img(img_);
+        typedef typename image_traits<image_type>::pixel_type ptype;
 
         dets.clear();
         if (max_dets == 0)
@@ -269,7 +270,7 @@ namespace dlib
 
 
 
-        typedef typename image_array_type::type::type pixel_type;
+        typedef typename image_traits<typename image_array_type::type>::pixel_type pixel_type;
         typedef typename promote<pixel_type>::type ptype;
 
         array2d<ptype> accum(images[0].nr(), images[0].nc());
@@ -338,7 +339,7 @@ namespace dlib
         if (movable_rects.size() == 0 && fixed_rects.size() == 0)
             return;
 
-        typedef typename image_array_type::type::type pixel_type;
+        typedef typename image_traits<typename image_array_type::type>::pixel_type pixel_type;
         typedef typename promote<pixel_type>::type ptype;
 
         array2d<ptype> accum(images[0].nr(), images[0].nc());

dlib/image_processing/scan_image_abstract.h

@@ -21,7 +21,8 @@ namespace dlib
     /*!
         requires
             - image_array_type       == an implementation of array/array_kernel_abstract.h
-            - image_array_type::type == an implementation of array2d/array2d_kernel_abstract.h
+            - image_array_type::type == an image object that implements the interface
+              defined in dlib/image_processing/generic_image.h 
         ensures
             - if (all elements of images have the same dimensions (i.e. 
               for all i and j: get_rect(images[i]) == get_rect(images[j]))) then
@@ -43,8 +44,9 @@ namespace dlib
     /*!
         requires
             - image_array_type             == an implementation of array/array_kernel_abstract.h
-            - image_array_type::type       == an implementation of array2d/array2d_kernel_abstract.h
-            - image_array_type::type::type == a scalar pixel type (e.g. int rather than rgb_pixel)
+            - image_array_type::type       == an image object that implements the interface
+              defined in dlib/image_processing/generic_image.h.  Moreover, these objects must
+              contain a scalar pixel type (e.g. int rather than rgb_pixel)
             - all_images_same_size(images) == true
             - for all valid i: rects[i].first < images.size()
               (i.e. all the rectangles must reference valid elements of images)
@@ -70,8 +72,9 @@ namespace dlib
     /*!
         requires
             - image_array_type             == an implementation of array/array_kernel_abstract.h
-            - image_array_type::type       == an implementation of array2d/array2d_kernel_abstract.h
-            - image_array_type::type::type == a scalar pixel type (e.g. int rather than rgb_pixel)
+            - image_array_type::type       == an image object that implements the interface
+              defined in dlib/image_processing/generic_image.h.  Moreover, these objects must
+              contain a scalar pixel type (e.g. int rather than rgb_pixel)
             - all_images_same_size(images) == true
             - center(window) == point(0,0)
             - for all valid i: 
@@ -109,8 +112,9 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == an implementation of array2d/array2d_kernel_abstract.h
-            - image_type::type == a scalar pixel type (e.g. int rather than rgb_pixel)
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h.  Moreover, these it must contain a
+              scalar pixel type (e.g. int rather than rgb_pixel)
         ensures
             - #dets == a list of points from img which had pixel values >= thresh.  
             - Specifically, we have:
@@ -142,8 +146,9 @@ namespace dlib
     /*!
         requires
             - image_array_type             == an implementation of array/array_kernel_abstract.h
-            - image_array_type::type       == an implementation of array2d/array2d_kernel_abstract.h
-            - image_array_type::type::type == a scalar pixel type (e.g. int rather than rgb_pixel)
+            - image_array_type::type       == an image object that implements the interface
+              defined in dlib/image_processing/generic_image.h.  Moreover, these objects must
+              contain a scalar pixel type (e.g. int rather than rgb_pixel)
             - images.size() > 0
             - rects.size() > 0 
             - all_images_same_size(images) == true
@@ -179,8 +184,9 @@ namespace dlib
     /*!
         requires
             - image_array_type             == an implementation of array/array_kernel_abstract.h
-            - image_array_type::type       == an implementation of array2d/array2d_kernel_abstract.h
-            - image_array_type::type::type == a scalar pixel type (e.g. int rather than rgb_pixel)
+            - image_array_type::type       == an image object that implements the interface
+              defined in dlib/image_processing/generic_image.h.  Moreover, these objects must
+              contain a scalar pixel type (e.g. int rather than rgb_pixel)
             - images.size() > 0
             - all_images_same_size(images) == true
             - center(window) == point(0,0)

dlib/image_processing/scan_image_pyramid.h

@@ -10,6 +10,7 @@
 #include "../array2d.h"
 #include <vector>
 #include "full_object_detection.h"
+#include "../image_processing/generic_image.h"
 
 namespace dlib
 {

dlib/image_processing/scan_image_pyramid_abstract.h

@@ -127,9 +127,9 @@ namespace dlib
                 - image_type must be a type with the following properties:
                     - image_type is default constructable.
                     - image_type is swappable by the global swap() function.
-                    - image_type logically represents some kind of image and therefore
-                      has .nr() and .nc() member functions.  .nr() should return the
-                      number of rows while .nc() returns the number of columns.
+                    - image_type logically represents some kind of image and therefore its
+                      number of rows and columns can be queried via num_rows(img) and
+                      num_columns(img) respectively.
                     - image_type objects can be loaded into Feature_extractor_type
                       objects via Feature_extractor_type::load().
                     - image_type objects can be used with Pyramid_type.  That is,

dlib/image_saver/image_saver.h

@@ -33,7 +33,7 @@ namespace dlib
 
     template <
         typename image_type,
-        bool grayscale = pixel_traits<typename image_type::type>::grayscale
+        bool grayscale = pixel_traits<typename image_traits<image_type>::pixel_type>::grayscale
         >
     struct save_bmp_helper;
 
@@ -42,10 +42,11 @@ namespace dlib
     struct save_bmp_helper<image_type,false>
     {
         static void save_bmp (
-            const image_type& image,
+            const image_type& image_,
             std::ostream& out 
         )
         {
+            const_image_view<image_type> image(image_);
             // we are going to write out a 24bit color image.
             byte_orderer::kernel_1a bo;
 
@@ -133,10 +134,11 @@ namespace dlib
     struct save_bmp_helper<image_type,true>
     {
         static void save_bmp (
-            const image_type& image,
+            const image_type& image_,
             std::ostream& out
         )
         {
+            const_image_view<image_type> image(image_);
             // we are going to write out an 8bit color image.
             byte_orderer::kernel_1a bo;
 
@@ -256,20 +258,9 @@ namespace dlib
 
     namespace dng_helpers_namespace
     {
-
         template <
             typename image_type,
-            int pixel_type = static_switch <
-                pixel_traits<typename image_type::type>::grayscale && sizeof(typename image_type::type) == 1,
-                pixel_traits<typename image_type::type>::rgb,
-                pixel_traits<typename image_type::type>::hsi,
-                false,
-                pixel_traits<typename image_type::type>::rgb_alpha,
-                false,
-                pixel_traits<typename image_type::type>::grayscale && sizeof(typename image_type::type) != 1 && 
-                    !is_float_type<typename image_type::type>::value,
-                is_float_type<typename image_type::type>::value
-                >::value
+            typename enabled = void
             >
         struct save_dng_helper;
 
@@ -279,13 +270,14 @@ namespace dlib
         typedef entropy_encoder_model<256,encoder_type>::kernel_4a eem_exp_type; 
 
         template <typename image_type >
-        struct save_dng_helper<image_type, grayscale_float>
+        struct save_dng_helper<image_type, typename enable_if<is_float_type<typename image_traits<image_type>::pixel_type> >::type >
         {
             static void save_dng (
-                const image_type& image,
+                const image_type& image_,
                 std::ostream& out 
             )
             {
+                const_image_view<image_type> image(image_);
                 out.write("DNG",3);
                 unsigned long version = 1;
                 serialize(version,out);
@@ -334,14 +326,24 @@ namespace dlib
         };
 
 
+        template <typename image_type>
+        struct is_non_float_non8bit_grayscale
+        {
+            typedef typename image_traits<image_type>::pixel_type pixel_type;
+            const static bool value = pixel_traits<pixel_type>::grayscale && 
+                                      sizeof(pixel_type) != 1 && 
+                                      !is_float_type<pixel_type>::value;
+        };
+
         template <typename image_type >
-        struct save_dng_helper<image_type, grayscale_16bit>
+        struct save_dng_helper<image_type, typename enable_if<is_non_float_non8bit_grayscale<image_type> >::type>
         {
             static void save_dng (
-                const image_type& image,
+                const image_type& image_,
                 std::ostream& out 
             )
             {
+                const_image_view<image_type> image(image_);
                 out.write("DNG",3);
                 unsigned long version = 1;
                 serialize(version,out);
@@ -375,15 +377,22 @@ namespace dlib
             }
         };
 
+        template <typename image_type>
+        struct is_8bit_grayscale
+        {
+            typedef typename image_traits<image_type>::pixel_type pixel_type;
+            const static bool value = pixel_traits<pixel_type>::grayscale && sizeof(pixel_type) == 1;
+        };
 
         template <typename image_type>
-        struct save_dng_helper<image_type, grayscale>
+        struct save_dng_helper<image_type, typename enable_if<is_8bit_grayscale<image_type> >::type>
         {
             static void save_dng (
-                const image_type& image,
+                const image_type& image_,
                 std::ostream& out 
             )
             {
+                const_image_view<image_type> image(image_);
                 out.write("DNG",3);
                 unsigned long version = 1;
                 serialize(version,out);
@@ -415,13 +424,21 @@ namespace dlib
         };
 
         template <typename image_type>
-        struct save_dng_helper<image_type,rgb>
+        struct is_rgb_image
+        {
+            typedef typename image_traits<image_type>::pixel_type pixel_type;
+            const static bool value = pixel_traits<pixel_type>::rgb;
+        };
+
+        template <typename image_type>
+        struct save_dng_helper<image_type,typename enable_if<is_rgb_image<image_type> >::type>
         {
             static void save_dng (
-                const image_type& image,
+                const image_type& image_,
                 std::ostream& out
             )
             {
+                const_image_view<image_type> image(image_);
                 out.write("DNG",3);
                 unsigned long version = 1;
                 serialize(version,out);
@@ -480,13 +497,21 @@ namespace dlib
         };
 
         template <typename image_type>
-        struct save_dng_helper<image_type,rgb_alpha>
+        struct is_rgb_alpha_image
+        {
+            typedef typename image_traits<image_type>::pixel_type pixel_type;
+            const static bool value = pixel_traits<pixel_type>::rgb_alpha;
+        };
+
+        template <typename image_type>
+        struct save_dng_helper<image_type,typename enable_if<is_rgb_alpha_image<image_type> >::type>
         {
             static void save_dng (
-                const image_type& image,
+                const image_type& image_,
                 std::ostream& out
             )
             {
+                const_image_view<image_type> image(image_);
                 out.write("DNG",3);
                 unsigned long version = 1;
                 serialize(version,out);
@@ -547,13 +572,21 @@ namespace dlib
         };
 
         template <typename image_type>
-        struct save_dng_helper<image_type,hsi>
+        struct is_hsi_image
+        {
+            typedef typename image_traits<image_type>::pixel_type pixel_type;
+            const static bool value = pixel_traits<pixel_type>::hsi;
+        };
+
+        template <typename image_type>
+        struct save_dng_helper<image_type,typename enable_if<is_hsi_image<image_type> >::type>
         {
             static void save_dng (
-                const image_type& image,
+                const image_type& image_,
                 std::ostream& out
             )
             {
+                const_image_view<image_type> image(image_);
                 out.write("DNG",3);
                 unsigned long version = 1;
                 serialize(version,out);

dlib/image_saver/image_saver_abstract.h

@@ -29,9 +29,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h or
-              a dlib::matrix
-            - pixel_traits<typename image_type::type> is defined  
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h or any kind of matrix expression.
         ensures
             - writes the image to the out stream in the Microsoft Windows BMP format.
             - image[0][0] will be in the upper left corner of the image.
@@ -58,9 +57,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h or
-              a dlib::matrix
-            - pixel_traits<typename image_type::type> is defined  
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h or any kind of matrix expression.
         ensures
             - opens the file indicated by file_name with an output file stream named fout
               and performs:
@@ -85,9 +83,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h or
-              a dlib::matrix
-            - pixel_traits<typename image_type::type> is defined  
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h or any kind of matrix expression.
         ensures
             - writes the image to the out stream in the dlib dng format.
             - image[0][0] will be in the upper left corner of the image.
@@ -114,9 +111,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h or
-              a dlib::matrix
-            - pixel_traits<typename image_type::type> is defined  
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h or any kind of matrix expression.
         ensures
             - opens the file indicated by file_name with an output file stream named fout 
               and performs:

dlib/image_saver/save_png.h

@@ -41,10 +41,12 @@ namespace dlib
         typename image_type
         >
     typename disable_if<is_matrix<image_type> >::type save_png(
-        const image_type& img,
+        const image_type& img_,
         const std::string& file_name
     )
     {
+        const_image_view<image_type> img(img_);
+
         // make sure requires clause is not broken
         DLIB_CASSERT(img.size() != 0,
             "\t save_png()"
@@ -62,7 +64,7 @@ namespace dlib
             COMPILE_TIME_ASSERT(sizeof(image_type) == 0);
 #else
         std::vector<unsigned char*> row_pointers(img.nr());
-        typedef typename image_type::type pixel_type;
+        typedef typename image_traits<image_type>::pixel_type pixel_type;
 
         if (is_same_type<rgb_pixel,pixel_type>::value)
         {
@@ -82,7 +84,7 @@ namespace dlib
         {
             // convert from HSI to RGB (Or potentially RGB pixels that aren't laid out as R G B)
             array2d<rgb_pixel> temp_img;
-            assign_image(temp_img, img);
+            assign_image(temp_img, img_);
             for (unsigned long i = 0; i < row_pointers.size(); ++i)
                 row_pointers[i] = (unsigned char*)(&temp_img[i][0]);
 
@@ -92,7 +94,7 @@ namespace dlib
         {
             // convert from RGBA pixels that aren't laid out as R G B A
             array2d<rgb_alpha_pixel> temp_img;
-            assign_image(temp_img, img);
+            assign_image(temp_img, img_);
             for (unsigned long i = 0; i < row_pointers.size(); ++i)
                 row_pointers[i] = (unsigned char*)(&temp_img[i][0]);
 
@@ -120,7 +122,7 @@ namespace dlib
             {
                 // convert from whatever this is to 16bit grayscale 
                 array2d<dlib::uint16> temp_img;
-                assign_image(temp_img, img);
+                assign_image(temp_img, img_);
                 for (unsigned long i = 0; i < row_pointers.size(); ++i)
                     row_pointers[i] = (unsigned char*)(&temp_img[i][0]);
 

dlib/image_saver/save_png_abstract.h

@@ -19,9 +19,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h or
-              a dlib::matrix
-            - pixel_traits<typename image_type::type> is defined  
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h or a matrix expression
             - image.size() != 0
         ensures
             - writes the image to the file indicated by file_name in the PNG (Portable Network Graphics) 

dlib/image_transforms/assign_image.h

@@ -10,36 +10,6 @@
 namespace dlib
 {
 
-// ----------------------------------------------------------------------------------------
-
-    template <
-        typename dest_image_type,
-        typename src_pixel_type
-        >
-    typename enable_if<is_matrix<dest_image_type> >::type impl_assign_single_pixel (
-        dest_image_type& img,
-        long r,
-        long c,
-        const src_pixel_type& pix
-    )
-    {
-        assign_pixel(img(r,c), pix);
-    }
-
-    template <
-        typename dest_image_type,
-        typename src_pixel_type
-        >
-    typename disable_if<is_matrix<dest_image_type> >::type impl_assign_single_pixel (
-        dest_image_type& img,
-        long r,
-        long c,
-        const src_pixel_type& pix
-    )
-    {
-        assign_pixel(img[r][c], pix);
-    }
-
 // ----------------------------------------------------------------------------------------
 
     template <
@@ -47,21 +17,33 @@ namespace dlib
         typename src_image_type
         >
     void impl_assign_image (
-        dest_image_type& dest,
+        image_view<dest_image_type>& dest,
         const src_image_type& src
     )
     {
         dest.set_size(src.nr(),src.nc());
-
         for (long r = 0; r < src.nr(); ++r)
         {
             for (long c = 0; c < src.nc(); ++c)
             {
-                impl_assign_single_pixel(dest,r,c, src(r,c));
+                assign_pixel(dest[r][c], src(r,c));
             }
         }
     }
 
+    template <
+        typename dest_image_type,
+        typename src_image_type
+        >
+    void impl_assign_image (
+        dest_image_type& dest_,
+        const src_image_type& src
+    )
+    {
+        image_view<dest_image_type> dest(dest_);
+        impl_assign_image(dest, src);
+    }
+
     template <
         typename dest_image_type,
         typename src_image_type
@@ -85,9 +67,9 @@ namespace dlib
         typename src_image_type
         >
     void impl_assign_image_scaled (
-        dest_image_type& dest,
+        image_view<dest_image_type>& dest,
         const src_image_type& src,
-        const double thresh = 4
+        const double thresh 
     )
     {
         DLIB_ASSERT( thresh > 0,
@@ -96,12 +78,15 @@ namespace dlib
             << "\n\t thresh: " << thresh 
             );
 
+
+        typedef typename image_traits<dest_image_type>::pixel_type dest_pixel;
+
         // If the destination has a dynamic range big enough to contain the source image data then just do a 
         // regular assign_image()
-        if (pixel_traits<typename dest_image_type::type>::max() >= pixel_traits<typename src_image_type::type>::max() &&
-            pixel_traits<typename dest_image_type::type>::min() <= pixel_traits<typename src_image_type::type>::min() )
+        if (pixel_traits<dest_pixel>::max() >= pixel_traits<typename src_image_type::type>::max() &&
+            pixel_traits<dest_pixel>::min() <= pixel_traits<typename src_image_type::type>::min() )
         {
-            assign_image(dest, src);
+            impl_assign_image(dest, src);
             return;
         }
 
@@ -112,7 +97,7 @@ namespace dlib
 
         if (src.size() == 1)
         {
-            impl_assign_single_pixel(dest,0,0, src(0,0));
+            impl_assign_image(dest, src);
             return;
         }
 
@@ -131,8 +116,8 @@ namespace dlib
         {
             // If the destination has a dynamic range big enough to contain the source image data then just do a 
             // regular assign_image()
-            if (pixel_traits<typename dest_image_type::type>::max() >= rs.max() &&
-                pixel_traits<typename dest_image_type::type>::min() <= rs.min() )
+            if (pixel_traits<dest_pixel>::max() >= rs.max() &&
+                pixel_traits<dest_pixel>::min() <= rs.min() )
             {
                 impl_assign_image(dest, src);
                 return;
@@ -145,8 +130,8 @@ namespace dlib
         const double lower = std::max(rs.mean() - thresh*rs.stddev(), rs.min());
 
 
-        const double dest_min = pixel_traits<typename dest_image_type::type>::min();
-        const double dest_max = pixel_traits<typename dest_image_type::type>::max();
+        const double dest_min = pixel_traits<dest_pixel>::min();
+        const double dest_max = pixel_traits<dest_pixel>::max();
 
         const double scale = (upper!=lower)? ((dest_max - dest_min) / (upper - lower)) : 0;
 
@@ -156,11 +141,25 @@ namespace dlib
             {
                 const double val = get_pixel_intensity(src(r,c)) - lower;
 
-                impl_assign_single_pixel(dest,r,c, scale*val + dest_min);
+                assign_pixel(dest[r][c], scale*val + dest_min);
             }
         }
     }
 
+    template <
+        typename dest_image_type,
+        typename src_image_type
+        >
+    void impl_assign_image_scaled (
+        dest_image_type& dest_,
+        const src_image_type& src,
+        const double thresh 
+    )
+    {
+        image_view<dest_image_type> dest(dest_);
+        impl_assign_image_scaled(dest, src, thresh);
+    }
+
     template <
         typename dest_image_type,
         typename src_image_type
@@ -185,7 +184,7 @@ namespace dlib
         typename src_pixel_type
         >
     void assign_all_pixels (
-        dest_image_type& dest_img,
+        image_view<dest_image_type>& dest_img,
         const src_pixel_type& src_pixel
     )
     {
@@ -198,16 +197,31 @@ namespace dlib
         }
     }
 
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename dest_image_type,
+        typename src_pixel_type
+        >
+    void assign_all_pixels (
+        dest_image_type& dest_img_,
+        const src_pixel_type& src_pixel
+    )
+    {
+        image_view<dest_image_type> dest_img(dest_img_);
+        assign_all_pixels(dest_img, src_pixel);
+    }
+
 // ----------------------------------------------------------------------------------------
 
     template <
         typename image_type
         >
     void assign_border_pixels (
-        image_type& img,
+        image_view<image_type>& img,
         long x_border_size,
         long y_border_size,
-        const typename image_type::type& p
+        const typename image_traits<image_type>::pixel_type& p
     )
     {
         DLIB_ASSERT( x_border_size >= 0 && y_border_size >= 0,
@@ -251,6 +265,20 @@ namespace dlib
         }
     }
 
+    template <
+        typename image_type
+        >
+    void assign_border_pixels (
+        image_type& img_,
+        long x_border_size,
+        long y_border_size,
+        const typename image_traits<image_type>::pixel_type& p
+    )
+    {
+        image_view<image_type> img(img_);
+        assign_border_pixels(img, x_border_size, y_border_size, p);
+    }
+
 // ----------------------------------------------------------------------------------------
 
     template <
@@ -269,7 +297,7 @@ namespace dlib
             << "\n\ty_border_size: " << y_border_size
             );
 
-        typename image_type::type zero_pixel;
+        typename image_traits<image_type>::pixel_type zero_pixel;
         assign_pixel_intensity(zero_pixel, 0);
         assign_border_pixels(img, x_border_size, y_border_size, zero_pixel);
     }
@@ -280,7 +308,30 @@ namespace dlib
         typename image_type
         >
     void zero_border_pixels (
-        image_type& img,
+        image_view<image_type>& img,
+        long x_border_size,
+        long y_border_size
+    )
+    {
+        DLIB_ASSERT( x_border_size >= 0 && y_border_size >= 0,
+            "\tvoid zero_border_pixels(img, p, border_size)"
+            << "\n\tYou have given an invalid border_size"
+            << "\n\tx_border_size: " << x_border_size
+            << "\n\ty_border_size: " << y_border_size
+            );
+
+        typename image_traits<image_type>::pixel_type zero_pixel;
+        assign_pixel_intensity(zero_pixel, 0);
+        assign_border_pixels(img, x_border_size, y_border_size, zero_pixel);
+    }
+
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename image_type
+        >
+    void zero_border_pixels (
+        image_view<image_type>& img,
         rectangle inside
     )
     {
@@ -307,6 +358,20 @@ namespace dlib
         }
     }
 
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename image_type
+        >
+    void zero_border_pixels (
+        image_type& img_,
+        const rectangle& inside
+    )
+    {
+        image_view<image_type> img(img_);
+        zero_border_pixels(img, inside);
+    }
+
 // ----------------------------------------------------------------------------------------
 
 }

dlib/image_transforms/assign_image_abstract.h

@@ -20,12 +20,11 @@ namespace dlib
     );
     /*!
         requires
-            - src_image_type == is an implementation of array2d/array2d_kernel_abstract.h or
-              a dlib::matrix or something convertible to a matrix via mat()
-            - dest_image_type == is an implementation of array2d/array2d_kernel_abstract.h or
-              is a dlib::matrix.
-            - pixel_traits<typename src_image_type::type> is defined  
-            - pixel_traits<typename dest_image_type::type> is defined  
+            - src_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h or any object convertible to a matrix
+              via mat().
+            - dest_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h or an image_view.
         ensures
             - #dest_img.nc() == src_img.nc()
             - #dest_img.nr() == src_img.nr()
@@ -47,12 +46,11 @@ namespace dlib
     );
     /*!
         requires
-            - src_image_type == is an implementation of array2d/array2d_kernel_abstract.h or
-              a dlib::matrix or something convertible to a matrix via mat()
-            - dest_image_type == is an implementation of array2d/array2d_kernel_abstract.h or
-              is a dlib::matrix.
-            - pixel_traits<typename src_image_type::type> is defined  
-            - pixel_traits<typename dest_image_type::type> is defined  
+            - src_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h or any object convertible to a matrix
+              via mat().
+            - dest_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h or an image_view.
             - thresh > 0
         ensures
             - #dest_img.nc() == src_img.nc()
@@ -77,8 +75,8 @@ namespace dlib
                       the following mapping:
                         let SRC_UPPER  = min(M + thresh*D, max(mat(src_img)))
                         let SRC_LOWER  = max(M - thresh*D, min(mat(src_img)))
-                        let DEST_UPPER = pixel_traits<dest_image_type::type>::max()
-                        let DEST_LOWER = pixel_traits<dest_image_type::type>::min()
+                        let DEST_UPPER = pixel_traits<image_traits<dest_image_type>::pixel_type>::max()
+                        let DEST_LOWER = pixel_traits<image_traits<dest_image_type>::pixel_type>::min()
 
                         MAPPING: [SRC_LOWER, SRC_UPPER] -> [DEST_LOWER, DEST_UPPER]
 
@@ -101,8 +99,8 @@ namespace dlib
     );
     /*!
         requires
-            - dest_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename dest_image_type::type> is defined  
+            - dest_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h or an image_view.
             - pixel_traits<src_pixel_type> is defined  
         ensures
             - #dest_img.nc() == dest_img.nc()
@@ -122,11 +120,12 @@ namespace dlib
         image_type& img,
         long x_border_size,
         long y_border_size,
-        const typename image_type::type& p
+        const typename image_traits<image_type>::pixel_type& p
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h or an image_view
             - x_border_size >= 0
             - y_border_size >= 0
         ensures
@@ -151,10 +150,10 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h or an image_view
             - x_border_size >= 0
             - y_border_size >= 0
-            - pixel_traits<typename image_type::type> is defined  
         ensures
             - #img.nc() == img.nc()
             - #img.nr() == img.nr()
@@ -176,8 +175,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type::type> is defined  
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h or an image_view
         ensures
             - #img.nc() == img.nc()
             - #img.nr() == img.nr()

dlib/image_transforms/colormaps.h

@@ -25,7 +25,7 @@ namespace dlib
         const static long NC = 0;
         typedef rgb_pixel type;
         typedef const rgb_pixel const_ret_type;
-        typedef typename T::mem_manager_type mem_manager_type;
+        typedef default_memory_manager mem_manager_type;
         typedef row_major_layout layout_type;
 
         const_ret_type apply (long r, long c ) const 
@@ -47,8 +47,8 @@ namespace dlib
             }
         }
 
-        long nr () const { return img.nr(); }
-        long nc () const { return img.nc(); }
+        long nr () const { return num_rows(img); }
+        long nc () const { return num_columns(img); }
     }; 
 
     template <
@@ -84,7 +84,7 @@ namespace dlib
         const static long NC = 0;
         typedef rgb_pixel type;
         typedef const rgb_pixel const_ret_type;
-        typedef typename T::mem_manager_type mem_manager_type;
+        typedef default_memory_manager mem_manager_type;
         typedef row_major_layout layout_type;
 
         const_ret_type apply (long r, long c ) const 
@@ -107,8 +107,8 @@ namespace dlib
             return pix;
         }
 
-        long nr () const { return img.nr(); }
-        long nc () const { return img.nc(); }
+        long nr () const { return num_rows(img); }
+        long nc () const { return num_columns(img); }
     }; 
 
     template <
@@ -158,7 +158,7 @@ namespace dlib
         const static long NC = 0;
         typedef rgb_pixel type;
         typedef const rgb_pixel const_ret_type;
-        typedef typename T::mem_manager_type mem_manager_type;
+        typedef default_memory_manager mem_manager_type;
         typedef row_major_layout layout_type;
 
         const_ret_type apply (long r, long c ) const 
@@ -203,8 +203,8 @@ namespace dlib
             return pix;
         }
 
-        long nr () const { return img.nr(); }
-        long nc () const { return img.nc(); }
+        long nr () const { return num_rows(img); }
+        long nc () const { return num_columns(img); }
     }; 
 
     template <

dlib/image_transforms/colormaps_abstract.h

@@ -21,9 +21,9 @@ namespace dlib
     );
     /*!
         requires
-            - image_type is an implementation of array2d/array2d_kernel_abstract.h, a
-              dlib::matrix, or something convertible to a matrix via mat().
-            - pixel_traits<image_type::type> must be defined
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h, or something convertible to a matrix
+              via mat().
         ensures
             - randomly generates a mapping from gray level pixel values
               to the RGB pixel space and then uses this mapping to create
@@ -46,9 +46,9 @@ namespace dlib
     );
     /*!
         requires
-            - image_type is an implementation of array2d/array2d_kernel_abstract.h, a
-              dlib::matrix, or something convertible to a matrix via mat().
-            - pixel_traits<image_type::type> must be defined
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h, or something convertible to a matrix
+              via mat().
         ensures
             - Interprets img as a grayscale image and returns a new matrix
               which represents a colored version of img.  In particular, the
@@ -68,9 +68,9 @@ namespace dlib
     );
     /*!
         requires
-            - image_type is an implementation of array2d/array2d_kernel_abstract.h, a
-              dlib::matrix, or something convertible to a matrix via mat().
-            - pixel_traits<image_type::type> must be defined
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h, or something convertible to a matrix
+              via mat().
         ensures
             - returns heatmap(img, max(mat(img)), min(mat(img)))
     !*/
@@ -88,9 +88,9 @@ namespace dlib
     );
     /*!
         requires
-            - image_type is an implementation of array2d/array2d_kernel_abstract.h, a 
-              dlib::matrix, or something convertible to a matrix via mat().
-            - pixel_traits<image_type::type> must be defined
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h, or something convertible to a matrix
+              via mat().
         ensures
             - Interprets img as a grayscale image and returns a new matrix which represents
               a colored version of img.  In particular, the colors will depict img using a
@@ -110,9 +110,9 @@ namespace dlib
     );
     /*!
         requires
-            - image_type is an implementation of array2d/array2d_kernel_abstract.h, a
-              dlib::matrix, or something convertible to a matrix via mat().
-            - pixel_traits<image_type::type> must be defined
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h, or something convertible to a matrix
+              via mat().
         ensures
             - returns jet(img, max(mat(img)), min(mat(img)))
     !*/

dlib/image_transforms/draw.h

@@ -23,10 +23,11 @@ namespace dlib
         long y1,
         long x2,
         long y2,
-        image_type& c,
+        image_type& c_,
         const pixel_type& val
     ) 
     {
+        image_view<image_type> c(c_);
         if (x1 == x2)
         {
             // make sure y1 comes before y2
@@ -214,11 +215,12 @@ namespace dlib
         typename pixel_type
         >
     void fill_rect (
-        image_type& img,
+        image_type& img_,
         const rectangle& rect,
         const pixel_type& pixel
     )
     {
+        image_view<image_type> img(img_);
         rectangle area = rect.intersect(get_rect(img));
 
         for (long r = area.top(); r <= area.bottom(); ++r)
@@ -235,11 +237,11 @@ namespace dlib
     template <
         typename image_array_type
         >
-    matrix<typename image_array_type::value_type::type> tile_images (
+    matrix<typename image_traits<typename image_array_type::value_type>::pixel_type> tile_images (
         const image_array_type& images
     )
     {
-        typedef typename image_array_type::value_type::type T;
+        typedef typename image_traits<typename image_array_type::value_type>::pixel_type T;
 
         if (images.size() == 0)
             return matrix<T>();
@@ -252,8 +254,8 @@ namespace dlib
         long nc = 0;
         for (unsigned long i = 0; i < images.size(); ++i)
         {
-            nr = std::max(images[i].nr(), nr);
-            nc = std::max(images[i].nc(), nc);
+            nr = std::max(num_rows(images[i]), nr);
+            nc = std::max(num_columns(images[i]), nc);
         }
 
         matrix<T> temp(size_nr*nr, size_nc*nc);

dlib/image_transforms/draw_abstract.h

@@ -22,8 +22,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<pixel_type> is defined
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
         ensures
             - #img.nr() == img.nr() && #img.nc() == img.nc()
               (i.e. the dimensions of the input image are not changed)
@@ -48,8 +48,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<pixel_type> is defined
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
         ensures
             - performs draw_line(img, point(x1,y1), point(x2,y2), val)
     !*/
@@ -68,12 +68,13 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - pixel_traits<pixel_type> is defined
         ensures
             - Draws the given rectangle onto the image img.  It does this by calling
               draw_line() four times to draw the four sides of the rectangle.  
-            - The rectancle is drawn with the color given by val.
+            - The rectangle is drawn with the color given by val.
             - The drawn rectangle will have edges that are thickness pixels wide.
     !*/
 
@@ -90,6 +91,8 @@ namespace dlib
     );
     /*!
         requires
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - pixel_traits<pixel_type> is defined
         ensures
             - fills the area defined by rect in the given image with the given pixel value.
@@ -100,13 +103,13 @@ namespace dlib
     template <
         typename image_array_type
         >
-    matrix<typename image_array_type::value_type::type> tile_images (
+    matrix<typename image_traits<typename image_array_type::value_type>::pixel_type> tile_images (
         const image_array_type& images
     );
     /*!
         requires
-            - image_array_type is a dlib::array of array2d objects, each containing pixels
-              with a pixel_traits definition or any type with a compatible interface.
+            - image_array_type is a dlib::array of image objects where each image object
+              implements the interface defined in dlib/image_processing/generic_image.h 
         ensures
             - This function takes the given images and tiles them into a single large
               square image and returns this new big tiled image.  Therefore, it is a useful

dlib/image_transforms/edge_detector.h

@@ -101,19 +101,20 @@ namespace dlib
         typename out_image_type
         >
     void sobel_edge_detector (
-        const in_image_type& in_img,
-        out_image_type& horz,
-        out_image_type& vert
+        const in_image_type& in_img_,
+        out_image_type& horz_,
+        out_image_type& vert_
     )
     {
-        COMPILE_TIME_ASSERT(pixel_traits<typename out_image_type::type>::is_unsigned == false);
-        DLIB_ASSERT( !is_same_object(in_img,horz) && !is_same_object(in_img,vert) &&
-                     !is_same_object(horz,vert),
-            "\tvoid sobel_edge_detector(in_img, horz, vert)"
+        typedef typename image_traits<out_image_type>::pixel_type pixel_type;
+        COMPILE_TIME_ASSERT(pixel_traits<pixel_type>::is_unsigned == false);
+        DLIB_ASSERT( !is_same_object(in_img_,horz_) && !is_same_object(in_img_,vert_) &&
+                     !is_same_object(horz_,vert_),
+            "\tvoid sobel_edge_detector(in_img_, horz_, vert_)"
             << "\n\t You can't give the same image as more than one argument"
-            << "\n\t is_same_object(in_img,horz): " << is_same_object(in_img,horz)
-            << "\n\t is_same_object(in_img,vert): " << is_same_object(in_img,vert)
-            << "\n\t is_same_object(horz,vert):    " << is_same_object(horz,vert)
+            << "\n\t is_same_object(in_img_,horz_): " << is_same_object(in_img_,horz_)
+            << "\n\t is_same_object(in_img_,vert_): " << is_same_object(in_img_,vert_)
+            << "\n\t is_same_object(horz_,vert_):    " << is_same_object(horz_,vert_)
             );
 
 
@@ -127,6 +128,11 @@ namespace dlib
         const long M = 3;
         const long N = 3;
 
+
+        const_image_view<in_image_type> in_img(in_img_);
+        image_view<out_image_type> horz(horz_);
+        image_view<out_image_type> vert(vert_);
+
         horz.set_size(in_img.nr(),in_img.nc());
         vert.set_size(in_img.nr(),in_img.nc());
 
@@ -145,7 +151,7 @@ namespace dlib
         {
             for (long c = first_col; c < last_col; ++c)
             {
-                typedef typename pixel_traits<typename in_image_type::type>::basic_pixel_type bp_type;
+                typedef typename pixel_traits<typename image_traits<in_image_type>::pixel_type>::basic_pixel_type bp_type;
 
                 typename promote<bp_type>::type p, horz_temp, vert_temp;
                 horz_temp = 0;
@@ -185,12 +191,16 @@ namespace dlib
         typename out_image_type
         >
     void suppress_non_maximum_edges (
-        const in_image_type& horz,
-        const in_image_type& vert,
-        out_image_type& out_img
+        const in_image_type& horz_,
+        const in_image_type& vert_,
+        out_image_type& out_img_
     )
     {
-        COMPILE_TIME_ASSERT(is_signed_type<typename in_image_type::type>::value);
+        const_image_view<in_image_type> horz(horz_);
+        const_image_view<in_image_type> vert(vert_);
+        image_view<out_image_type> out_img(out_img_);
+
+        COMPILE_TIME_ASSERT(is_signed_type<typename image_traits<in_image_type>::pixel_type>::value);
         DLIB_ASSERT( horz.nr() == vert.nr() && horz.nc() == vert.nc(),
             "\tvoid suppress_non_maximum_edges(horz, vert, out_img)"
             << "\n\tYou have to give horz and vert gradient images that are the same size"
@@ -199,11 +209,11 @@ namespace dlib
             << "\n\tvert.nr():   " << vert.nr() 
             << "\n\tvert.nc():   " << vert.nc() 
             );
-        DLIB_ASSERT( !is_same_object(out_img,horz) && !is_same_object(out_img,vert),
-            "\tvoid suppress_non_maximum_edges(horz, vert, out_img)"
+        DLIB_ASSERT( !is_same_object(out_img_,horz_) && !is_same_object(out_img_,vert_),
+            "\tvoid suppress_non_maximum_edges(horz_, vert_, out_img_)"
             << "\n\t out_img can't be the same as one of the input images."
-            << "\n\t is_same_object(out_img,horz):    " << is_same_object(out_img,horz)
-            << "\n\t is_same_object(out_img,vert):    " << is_same_object(out_img,vert)
+            << "\n\t is_same_object(out_img_,horz_):    " << is_same_object(out_img_,horz_)
+            << "\n\t is_same_object(out_img_,vert_):    " << is_same_object(out_img_,vert_)
             );
 
         using std::min;
@@ -237,7 +247,7 @@ namespace dlib
         {
             for (long c = first_col; c < last_col; ++c)
             {
-                typedef typename promote<typename in_image_type::type>::type T;
+                typedef typename promote<typename image_traits<in_image_type>::pixel_type>::type T;
                 const T y = horz[r][c];
                 const T x = vert[r][c];
 

dlib/image_transforms/edge_detector_abstract.h

@@ -45,10 +45,11 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename in_image_type::type> must be defined
-            - pixel_traits<typename out_image_type::type>::is_unsigned == false
+            - in_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - out_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - out_image_type must use signed grayscale pixels
             - is_same_object(in_img,horz) == false
             - is_same_object(in_img,vert) == false
             - is_same_object(horz,vert) == false
@@ -79,14 +80,15 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename out_image_type::type> must be defined
+            - in_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - out_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - horz.nr() == vert.nr()
             - horz.nc() == vert.nc()
             - is_same_object(out_img, horz) == false
             - is_same_object(out_img, vert) == false
-            - in_image_type::type == A signed scalar type (e.g. int, double, etc.) 
+            - image_traits<in_image_type>::pixel_type == A signed scalar type (e.g. int, double, etc.) 
         ensures
             - #out_img.nr() = horz.nr()
             - #out_img.nc() = horz.nc()

dlib/image_transforms/equalize_histogram.h

@@ -21,24 +21,26 @@ namespace dlib
         typename MM
         >
     void get_histogram (
-        const in_image_type& in_img,
+        const in_image_type& in_img_,
         matrix<unsigned long,R,C,MM>& hist
     )
     {
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::is_unsigned == true );
+        typedef typename image_traits<in_image_type>::pixel_type pixel_type;
+        COMPILE_TIME_ASSERT( pixel_traits<pixel_type>::is_unsigned == true );
 
-        typedef typename pixel_traits<typename in_image_type::type>::basic_pixel_type in_image_basic_pixel_type;
+        typedef typename pixel_traits<pixel_type>::basic_pixel_type in_image_basic_pixel_type;
         COMPILE_TIME_ASSERT( sizeof(in_image_basic_pixel_type) <= 2);
 
         // make sure hist is the right size
         if (R == 1)
-            hist.set_size(1,pixel_traits<typename in_image_type::type>::max()+1);
+            hist.set_size(1,pixel_traits<pixel_type>::max()+1);
         else
-            hist.set_size(pixel_traits<typename in_image_type::type>::max()+1,1);
+            hist.set_size(pixel_traits<pixel_type>::max()+1,1);
 
 
         set_all_elements(hist,0);
 
+        const_image_view<in_image_type> in_img(in_img_);
         // compute the histogram 
         for (long r = 0; r < in_img.nr(); ++r)
         {
@@ -57,20 +59,25 @@ namespace dlib
         typename out_image_type 
         >
     void equalize_histogram (
-        const in_image_type& in_img,
-        out_image_type& out_img
+        const in_image_type& in_img_,
+        out_image_type& out_img_
     )
     {
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+        const_image_view<in_image_type> in_img(in_img_);
+        image_view<out_image_type> out_img(out_img_);
 
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::is_unsigned == true );
-        COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::is_unsigned == true );
+        typedef typename image_traits<in_image_type>::pixel_type in_pixel_type;
+        typedef typename image_traits<out_image_type>::pixel_type out_pixel_type;
 
-        typedef typename pixel_traits<typename in_image_type::type>::basic_pixel_type in_image_basic_pixel_type;
+        COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<out_pixel_type>::has_alpha == false );
+
+        COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type>::is_unsigned == true );
+        COMPILE_TIME_ASSERT( pixel_traits<out_pixel_type>::is_unsigned == true );
+
+        typedef typename pixel_traits<in_pixel_type>::basic_pixel_type in_image_basic_pixel_type;
         COMPILE_TIME_ASSERT( sizeof(in_image_basic_pixel_type) <= 2);
 
-        typedef typename out_image_type::type out_pixel_type;
 
         // if there isn't any input image then don't do anything
         if (in_img.size() == 0)
@@ -83,8 +90,9 @@ namespace dlib
 
         unsigned long p;
 
-        matrix<unsigned long,1,0,typename in_image_type::mem_manager_type> histogram;
-        get_histogram(in_img, histogram);
+        matrix<unsigned long,1,0> histogram;
+        get_histogram(in_img_, histogram);
+        in_img = in_img_;
 
         double scale = pixel_traits<out_pixel_type>::max();
         if (in_img.size() > histogram(0))

dlib/image_transforms/equalize_histogram_abstract.h

@@ -21,13 +21,16 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename in_image_type::type>::has_alpha == false
-            - pixel_traits<typename out_image_type::type>::has_alpha == false 
-            - pixel_traits<typename in_image_type::type>::is_unsigned == true 
-            - pixel_traits<typename out_image_type::type>::is_unsigned == true 
-            - pixel_traits<typename in_image_type::type>::max() <= 65535 
+            - in_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - out_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - Let pixel_type be the type of pixel in either input or output images, then we
+              must have:
+                - pixel_traits<pixel_type>::has_alpha == false
+                - pixel_traits<pixel_type>::is_unsigned == true 
+            - For the input image pixel type, we have the additional requirement that:
+                - pixel_traits<pixel_type>::max() <= 65535 
         ensures
             - #out_img == the histogram equalized version of in_img
             - #out_img.nc() == in_img.nc()
@@ -61,9 +64,11 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename in_image_type::type>::is_unsigned == true 
-            - pixel_traits<typename in_image_type::type>::max() <= 65535 
+            - in_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - Let pixel_type denote the type of pixel in in_img, then we must have:
+                - pixel_traits<pixel_type>::is_unsigned == true 
+                - pixel_traits<pixel_type>::max() <= 65535 
             - hist must be capable of representing a column vector of length 
               pixel_traits<typename in_image_type>::max(). I.e. if R and C are nonzero
               then they must be values that don't conflict with the previous sentence.

dlib/image_transforms/fhog.h

@@ -22,7 +22,7 @@ namespace dlib
     namespace impl_fhog
     {
         template <typename image_type>
-        inline typename dlib::enable_if_c<pixel_traits<typename image_type::type>::rgb>::type get_gradient (
+        inline typename dlib::enable_if_c<pixel_traits<typename image_type::pixel_type>::rgb>::type get_gradient (
             const int r,
             const int c,
             const image_type& img,
@@ -60,7 +60,7 @@ namespace dlib
         }
 
         template <typename image_type>
-        inline typename dlib::enable_if_c<pixel_traits<typename image_type::type>::rgb>::type get_gradient (
+        inline typename dlib::enable_if_c<pixel_traits<typename image_type::pixel_type>::rgb>::type get_gradient (
             const int r,
             const int c,
             const image_type& img,
@@ -145,7 +145,7 @@ namespace dlib
     // ------------------------------------------------------------------------------------
 
         template <typename image_type>
-        inline typename dlib::disable_if_c<pixel_traits<typename image_type::type>::rgb>::type get_gradient (
+        inline typename dlib::disable_if_c<pixel_traits<typename image_type::pixel_type>::rgb>::type get_gradient (
             const int r,
             const int c,
             const image_type& img,
@@ -159,7 +159,7 @@ namespace dlib
         }
 
         template <typename image_type>
-        inline typename dlib::disable_if_c<pixel_traits<typename image_type::type>::rgb>::type get_gradient (
+        inline typename dlib::disable_if_c<pixel_traits<typename image_type::pixel_type>::rgb>::type get_gradient (
             int r,
             int c,
             const image_type& img,
@@ -275,13 +275,14 @@ namespace dlib
             typename out_type
             >
         void impl_extract_fhog_features(
-            const image_type& img, 
+            const image_type& img_, 
             out_type& hog, 
             int cell_size,
             int filter_rows_padding,
             int filter_cols_padding
         ) 
         {
+            const_image_view<image_type> img(img_);
             // make sure requires clause is not broken
             DLIB_ASSERT( cell_size > 0 &&
                          filter_rows_padding > 0 &&

dlib/image_transforms/fhog_abstract.h

@@ -29,9 +29,8 @@ namespace dlib
             - cell_size > 0
             - filter_rows_padding > 0
             - filter_cols_padding > 0
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - img contains some kind of pixel type. 
-              (i.e. pixel_traits<typename image_type::type> is defined)
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - T should be float or double
         ensures
             - This function implements the HOG feature extraction method described in 
@@ -89,9 +88,8 @@ namespace dlib
             - cell_size > 0
             - filter_rows_padding > 0
             - filter_cols_padding > 0
-            - image_type  == is an implementation of array2d/array2d_kernel_abstract.h
-            - img contains some kind of pixel type. 
-              (i.e. pixel_traits<typename image_type::type> is defined)
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - T should be float or double
         ensures
             - This function is identical to the above extract_fhog_features() routine
@@ -124,9 +122,8 @@ namespace dlib
             - cell_size > 0
             - filter_rows_padding > 0
             - filter_cols_padding > 0
-            - image_type  == is an implementation of array2d/array2d_kernel_abstract.h
-            - img contains some kind of pixel type. 
-              (i.e. pixel_traits<typename image_type::type> is defined)
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
         ensures
             - This function calls the above extract_fhog_features() routine and simply
               packages the entire output into a dlib::matrix.  The matrix is constructed
@@ -158,9 +155,8 @@ namespace dlib
             - cell_size > 0
             - filter_rows_padding > 0
             - filter_cols_padding > 0
-            - image_type  == is an implementation of array2d/array2d_kernel_abstract.h
-            - img contains some kind of pixel type. 
-              (i.e. pixel_traits<typename image_type::type> is defined)
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - T is float, double, or long double
         ensures
             - This function is identical to the above version of extract_fhog_features()

dlib/image_transforms/image_pyramid.h

@@ -119,8 +119,10 @@ namespace dlib
                         << "\n\t this:                           " << this
                         );
 
-            COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-            COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+            typedef typename image_traits<in_image_type>::pixel_type in_pixel_type;
+            typedef typename image_traits<out_image_type>::pixel_type out_pixel_type;
+            COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type>::has_alpha == false );
+            COMPILE_TIME_ASSERT( pixel_traits<out_pixel_type>::has_alpha == false );
 
             down.clear();
         }
@@ -220,8 +222,9 @@ namespace dlib
             template <typename T, typename U>
             struct both_images_rgb
             {
-                const static bool value = pixel_traits<typename T::type>::rgb &&
-                                        pixel_traits<typename U::type>::rgb;
+                typedef typename image_traits<T>::pixel_type T_pix;
+                typedef typename image_traits<U>::pixel_type U_pix;
+                const static bool value = pixel_traits<T_pix>::rgb && pixel_traits<U_pix>::rgb;
             };
         public:
 
@@ -230,19 +233,24 @@ namespace dlib
                 typename out_image_type
                 >
             typename disable_if<both_images_rgb<in_image_type,out_image_type> >::type operator() (
-                const in_image_type& original,
-                out_image_type& down
+                const in_image_type& original_,
+                out_image_type& down_
             ) const
             {
                 // make sure requires clause is not broken
-                DLIB_ASSERT( is_same_object(original, down) == false, 
+                DLIB_ASSERT( is_same_object(original_, down_) == false, 
                             "\t void pyramid_down_2_1::operator()"
-                            << "\n\t is_same_object(original, down): " << is_same_object(original, down) 
+                            << "\n\t is_same_object(original_, down_): " << is_same_object(original_, down_) 
                             << "\n\t this:                           " << this
                             );
 
-                COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-                COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+                typedef typename image_traits<in_image_type>::pixel_type in_pixel_type;
+                typedef typename image_traits<out_image_type>::pixel_type out_pixel_type;
+                COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type>::has_alpha == false );
+                COMPILE_TIME_ASSERT( pixel_traits<out_pixel_type>::has_alpha == false );
+
+                const_image_view<in_image_type> original(original_);
+                image_view<out_image_type> down(down_);
 
                 if (original.nr() <= 8 || original.nc() <= 8)
                 {
@@ -250,7 +258,7 @@ namespace dlib
                     return;
                 }
 
-                typedef typename pixel_traits<typename in_image_type::type>::basic_pixel_type bp_type;
+                typedef typename pixel_traits<in_pixel_type>::basic_pixel_type bp_type;
                 typedef typename promote<bp_type>::type ptype;
                 array2d<ptype> temp_img;
                 temp_img.set_size(original.nr(), (original.nc()-3)/2);
@@ -326,19 +334,24 @@ namespace dlib
                 typename out_image_type
                 >
             typename enable_if<both_images_rgb<in_image_type,out_image_type> >::type operator() (
-                const in_image_type& original,
-                out_image_type& down
+                const in_image_type& original_,
+                out_image_type& down_
             ) const
             {
                 // make sure requires clause is not broken
-                DLIB_ASSERT( is_same_object(original, down) == false, 
+                DLIB_ASSERT( is_same_object(original_, down_) == false, 
                             "\t void pyramid_down_2_1::operator()"
-                            << "\n\t is_same_object(original, down): " << is_same_object(original, down) 
+                            << "\n\t is_same_object(original_, down_): " << is_same_object(original_, down_) 
                             << "\n\t this:                           " << this
                             );
 
-                COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-                COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+                typedef typename image_traits<in_image_type>::pixel_type in_pixel_type;
+                typedef typename image_traits<out_image_type>::pixel_type out_pixel_type;
+                COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type>::has_alpha == false );
+                COMPILE_TIME_ASSERT( pixel_traits<out_pixel_type>::has_alpha == false );
+
+                const_image_view<in_image_type> original(original_);
+                image_view<out_image_type> down(down_);
 
                 if (original.nr() <= 8 || original.nc() <= 8)
                 {
@@ -539,8 +552,9 @@ namespace dlib
             template <typename T, typename U>
             struct both_images_rgb
             {
-                const static bool value = pixel_traits<typename T::type>::rgb &&
-                                        pixel_traits<typename U::type>::rgb;
+                typedef typename image_traits<T>::pixel_type T_pix;
+                typedef typename image_traits<U>::pixel_type U_pix;
+                const static bool value = pixel_traits<T_pix>::rgb && pixel_traits<U_pix>::rgb;
             };
         public:
 
@@ -549,19 +563,24 @@ namespace dlib
                 typename out_image_type
                 >
             typename disable_if<both_images_rgb<in_image_type,out_image_type> >::type operator() (
-                const in_image_type& original,
-                out_image_type& down
+                const in_image_type& original_,
+                out_image_type& down_
             ) const
             {
                 // make sure requires clause is not broken
-                DLIB_ASSERT(is_same_object(original, down) == false, 
+                DLIB_ASSERT(is_same_object(original_, down_) == false, 
                             "\t void pyramid_down_3_2::operator()"
-                            << "\n\t is_same_object(original, down): " << is_same_object(original, down) 
+                            << "\n\t is_same_object(original_, down_): " << is_same_object(original_, down_) 
                             << "\n\t this:                           " << this
                             );
 
-                COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-                COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+                typedef typename image_traits<in_image_type>::pixel_type in_pixel_type;
+                typedef typename image_traits<out_image_type>::pixel_type out_pixel_type;
+                COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type>::has_alpha == false );
+                COMPILE_TIME_ASSERT( pixel_traits<out_pixel_type>::has_alpha == false );
+
+                const_image_view<in_image_type> original(original_);
+                image_view<out_image_type> down(down_);
 
                 if (original.nr() <= 8 || original.nc() <= 8)
                 {
@@ -572,7 +591,7 @@ namespace dlib
                 const long size_in = 3;
                 const long size_out = 2;
 
-                typedef typename pixel_traits<typename in_image_type::type>::basic_pixel_type bp_type;
+                typedef typename pixel_traits<in_pixel_type>::basic_pixel_type bp_type;
                 typedef typename promote<bp_type>::type ptype;
                 const long full_nr =  size_out*((original.nr()-2)/size_in);
                 const long part_nr = (size_out*(original.nr()-2))/size_in;
@@ -590,7 +609,7 @@ namespace dlib
                     for (c = 0; c < full_nc; c+=size_out)
                     {
                         ptype block[size_in][size_in];
-                        separable_3x3_filter_block_grayscale(block, original, rr, cc, 2, 12, 2);
+                        separable_3x3_filter_block_grayscale(block, original_, rr, cc, 2, 12, 2);
 
                         // bi-linearly interpolate block 
                         assign_pixel(down[r][c]     , (block[0][0]*9 + block[1][0]*3 + block[0][1]*3 + block[1][1])/(16*256));
@@ -603,7 +622,7 @@ namespace dlib
                     if (part_nc - full_nc == 1)
                     {
                         ptype block[size_in][2];
-                        separable_3x3_filter_block_grayscale(block, original, rr, cc, 2, 12, 2);
+                        separable_3x3_filter_block_grayscale(block, original_, rr, cc, 2, 12, 2);
 
                         // bi-linearly interpolate partial block 
                         assign_pixel(down[r][c]     , (block[0][0]*9 + block[1][0]*3 + block[0][1]*3 + block[1][1])/(16*256));
@@ -618,7 +637,7 @@ namespace dlib
                     for (c = 0; c < full_nc; c+=size_out)
                     {
                         ptype block[2][size_in];
-                        separable_3x3_filter_block_grayscale(block, original, rr, cc, 2, 12, 2);
+                        separable_3x3_filter_block_grayscale(block, original_, rr, cc, 2, 12, 2);
 
                         // bi-linearly interpolate partial block 
                         assign_pixel(down[r][c]     , (block[0][0]*9 + block[1][0]*3 + block[0][1]*3 + block[1][1])/(16*256));
@@ -629,7 +648,7 @@ namespace dlib
                     if (part_nc - full_nc == 1)
                     {
                         ptype block[2][2];
-                        separable_3x3_filter_block_grayscale(block, original, rr, cc, 2, 12, 2);
+                        separable_3x3_filter_block_grayscale(block, original_, rr, cc, 2, 12, 2);
 
                         // bi-linearly interpolate partial block 
                         assign_pixel(down[r][c]     , (block[0][0]*9 + block[1][0]*3 + block[0][1]*3 + block[1][1])/(16*256));
@@ -655,19 +674,24 @@ namespace dlib
                 typename out_image_type
                 >
             typename enable_if<both_images_rgb<in_image_type,out_image_type> >::type operator() (
-                const in_image_type& original,
-                out_image_type& down
+                const in_image_type& original_,
+                out_image_type& down_
             ) const
             {
                 // make sure requires clause is not broken
-                DLIB_ASSERT( is_same_object(original, down) == false, 
+                DLIB_ASSERT( is_same_object(original_, down_) == false, 
                             "\t void pyramid_down_3_2::operator()"
-                            << "\n\t is_same_object(original, down): " << is_same_object(original, down) 
+                            << "\n\t is_same_object(original_, down_): " << is_same_object(original_, down_) 
                             << "\n\t this:                           " << this
                             );
 
-                COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-                COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+                typedef typename image_traits<in_image_type>::pixel_type in_pixel_type;
+                typedef typename image_traits<out_image_type>::pixel_type out_pixel_type;
+                COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type>::has_alpha == false );
+                COMPILE_TIME_ASSERT( pixel_traits<out_pixel_type>::has_alpha == false );
+
+                const_image_view<in_image_type> original(original_);
+                image_view<out_image_type> down(down_);
 
                 if (original.nr() <= 8 || original.nc() <= 8)
                 {
@@ -694,7 +718,7 @@ namespace dlib
                     for (c = 0; c < full_nc; c+=size_out)
                     {
                         rgbptype block[size_in][size_in];
-                        separable_3x3_filter_block_rgb(block, original, rr, cc, 2, 12, 2);
+                        separable_3x3_filter_block_rgb(block, original_, rr, cc, 2, 12, 2);
 
                         // bi-linearly interpolate block 
                         down[r][c].red       = (block[0][0].red*9   + block[1][0].red*3   + block[0][1].red*3   + block[1][1].red)/(16*256);
@@ -718,7 +742,7 @@ namespace dlib
                     if (part_nc - full_nc == 1)
                     {
                         rgbptype block[size_in][2];
-                        separable_3x3_filter_block_rgb(block, original, rr, cc, 2, 12, 2);
+                        separable_3x3_filter_block_rgb(block, original_, rr, cc, 2, 12, 2);
 
                         // bi-linearly interpolate partial block 
                         down[r][c].red       = (block[0][0].red*9   + block[1][0].red*3   + block[0][1].red*3   + block[1][1].red)/(16*256);
@@ -738,7 +762,7 @@ namespace dlib
                     for (c = 0; c < full_nc; c+=size_out)
                     {
                         rgbptype block[2][size_in];
-                        separable_3x3_filter_block_rgb(block, original, rr, cc, 2, 12, 2);
+                        separable_3x3_filter_block_rgb(block, original_, rr, cc, 2, 12, 2);
 
                         // bi-linearly interpolate partial block 
                         down[r][c].red       = (block[0][0].red*9   + block[1][0].red*3   + block[0][1].red*3   + block[1][1].red)/(16*256);
@@ -754,7 +778,7 @@ namespace dlib
                     if (part_nc - full_nc == 1)
                     {
                         rgbptype block[2][2];
-                        separable_3x3_filter_block_rgb(block, original, rr, cc, 2, 12, 2);
+                        separable_3x3_filter_block_rgb(block, original_, rr, cc, 2, 12, 2);
 
                         // bi-linearly interpolate partial block 
                         down[r][c].red       = (block[0][0].red*9   + block[1][0].red*3   + block[0][1].red*3   + block[1][1].red)/(16*256);
@@ -878,12 +902,13 @@ namespace dlib
                         << "\n\t this:                           " << this
                         );
 
-            COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-            COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+            typedef typename image_traits<in_image_type>::pixel_type in_pixel_type;
+            typedef typename image_traits<out_image_type>::pixel_type out_pixel_type;
+            COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type>::has_alpha == false );
+            COMPILE_TIME_ASSERT( pixel_traits<out_pixel_type>::has_alpha == false );
 
 
-            down.set_size(((N-1)*original.nr())/N,
-                          ((N-1)*original.nc())/N);
+            set_image_size(down, ((N-1)*num_rows(original))/N, ((N-1)*num_columns(original))/N);
             resize_image(original, down);
         }
     };

dlib/image_transforms/image_pyramid_abstract.h

@@ -47,10 +47,12 @@ namespace dlib
         /*!
             requires
                 - is_same_object(original, down) == false
-                - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-                - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-                - pixel_traits<typename in_image_type::type>::has_alpha == false
-                - pixel_traits<typename out_image_type::type>::has_alpha == false
+                - in_image_type == an image object that implements the interface defined in
+                  dlib/image_processing/generic_image.h 
+                - out_image_type == an image object that implements the interface defined in
+                  dlib/image_processing/generic_image.h 
+                - for both pixel types P in the input and output images, we require:
+                    - pixel_traits<P>::has_alpha == false
             ensures
                 - #down will contain an image that is roughly (N-1)/N times the size of the
                   original image.  

dlib/image_transforms/integral_image.h

@@ -31,9 +31,10 @@ namespace dlib
 
         template <typename image_type>
         void load (
-            const image_type& img
+            const image_type& img_
         )
         {
+            const_image_view<image_type> img(img_);
             T pixel;
             int_img.set_size(img.nr(), img.nc());
 

dlib/image_transforms/integral_image_abstract.h

@@ -59,8 +59,10 @@ namespace dlib
         );
         /*!
             requires
-                - image_type == a type that implements the array2d/array2d_kernel_abstract.h interface
-                - pixel_traits<typename image_type::type>::has_alpha == false 
+                - image_type == an image object that implements the interface defined in
+                  dlib/image_processing/generic_image.h 
+                - Let P denote the type of pixel in img, then we require:
+                    - pixel_traits<P>::has_alpha == false 
             ensures
                 - #nr() == img.nr()
                 - #nc() == img.nc()

dlib/image_transforms/interpolation.h

@@ -20,14 +20,14 @@ namespace dlib
     {
     public:
 
-        template <typename image_type, typename pixel_type>
+        template <typename image_view_type, typename pixel_type>
         bool operator() (
-            const image_type& img,
+            const image_view_type& img,
             const dlib::point& p,
             pixel_type& result
         ) const
         {
-            COMPILE_TIME_ASSERT(pixel_traits<typename image_type::type>::has_alpha == false);
+            COMPILE_TIME_ASSERT(pixel_traits<typename image_view_type::pixel_type>::has_alpha == false);
 
             if (get_rect(img).contains(p))
             {
@@ -49,19 +49,19 @@ namespace dlib
         template <typename T>
         struct is_rgb_image 
         {
-            const static bool value = pixel_traits<typename T::type>::rgb;
+            const static bool value = pixel_traits<typename T::pixel_type>::rgb;
         };
 
     public:
 
-        template <typename T, typename image_type, typename pixel_type>
-        typename disable_if<is_rgb_image<image_type>,bool>::type operator() (
-            const image_type& img,
+        template <typename T, typename image_view_type, typename pixel_type>
+        typename disable_if<is_rgb_image<image_view_type>,bool>::type operator() (
+            const image_view_type& img,
             const dlib::vector<T,2>& p,
             pixel_type& result
         ) const
         {
-            COMPILE_TIME_ASSERT(pixel_traits<typename image_type::type>::has_alpha == false);
+            COMPILE_TIME_ASSERT(pixel_traits<typename image_view_type::pixel_type>::has_alpha == false);
 
             const long left   = static_cast<long>(std::floor(p.x()));
             const long top    = static_cast<long>(std::floor(p.y()));
@@ -90,14 +90,14 @@ namespace dlib
             return true;
         }
 
-        template <typename T, typename image_type, typename pixel_type>
-        typename enable_if<is_rgb_image<image_type>,bool>::type operator() (
-            const image_type& img,
+        template <typename T, typename image_view_type, typename pixel_type>
+        typename enable_if<is_rgb_image<image_view_type>,bool>::type operator() (
+            const image_view_type& img,
             const dlib::vector<T,2>& p,
             pixel_type& result
         ) const
         {
-            COMPILE_TIME_ASSERT(pixel_traits<typename image_type::type>::has_alpha == false);
+            COMPILE_TIME_ASSERT(pixel_traits<typename image_view_type::pixel_type>::has_alpha == false);
 
             const long left   = static_cast<long>(std::floor(p.x()));
             const long top    = static_cast<long>(std::floor(p.y()));
@@ -151,19 +151,19 @@ namespace dlib
         template <typename T>
         struct is_rgb_image 
         {
-            const static bool value = pixel_traits<typename T::type>::rgb;
+            const static bool value = pixel_traits<typename T::pixel_type>::rgb;
         };
 
     public:
 
-        template <typename T, typename image_type, typename pixel_type>
-        typename disable_if<is_rgb_image<image_type>,bool>::type operator() (
-            const image_type& img,
+        template <typename T, typename image_view_type, typename pixel_type>
+        typename disable_if<is_rgb_image<image_view_type>,bool>::type operator() (
+            const image_view_type& img,
             const dlib::vector<T,2>& p,
             pixel_type& result
         ) const
         {
-            COMPILE_TIME_ASSERT(pixel_traits<typename image_type::type>::has_alpha == false);
+            COMPILE_TIME_ASSERT(pixel_traits<typename image_view_type::pixel_type>::has_alpha == false);
 
             const point pp(p);
 
@@ -189,14 +189,14 @@ namespace dlib
             return true;
         }
 
-        template <typename T, typename image_type, typename pixel_type>
-        typename enable_if<is_rgb_image<image_type>,bool>::type operator() (
-            const image_type& img,
+        template <typename T, typename image_view_type, typename pixel_type>
+        typename enable_if<is_rgb_image<image_view_type>,bool>::type operator() (
+            const image_view_type& img,
             const dlib::vector<T,2>& p,
             pixel_type& result
         ) const
         {
-            COMPILE_TIME_ASSERT(pixel_traits<typename image_type::type>::has_alpha == false);
+            COMPILE_TIME_ASSERT(pixel_traits<typename image_view_type::pixel_type>::has_alpha == false);
 
             const point pp(p);
 
@@ -342,13 +342,15 @@ namespace dlib
             << "\n\t is_same_object(in_img, out_img):  " << is_same_object(in_img, out_img)
             );
 
+        const_image_view<image_type1> imgv(in_img);
+        image_view<image_type2> out_imgv(out_img);
 
         for (long r = area.top(); r <= area.bottom(); ++r)
         {
             for (long c = area.left(); c <= area.right(); ++c)
             {
-                if (!interp(in_img, map_point(dlib::vector<double,2>(c,r)), out_img[r][c]))
-                    set_background(out_img[r][c]);
+                if (!interp(imgv, map_point(dlib::vector<double,2>(c,r)), out_imgv[r][c]))
+                    set_background(out_imgv[r][c]);
             }
         }
     }
@@ -522,9 +524,9 @@ namespace dlib
 // ----------------------------------------------------------------------------------------
 
     template <typename image_type>
-    struct is_rgb_image { const static bool value = pixel_traits<typename image_type::type>::rgb; };
+    struct is_rgb_image { const static bool value = pixel_traits<typename image_traits<image_type>::pixel_type>::rgb; };
     template <typename image_type>
-    struct is_grayscale_image { const static bool value = pixel_traits<typename image_type::type>::grayscale; };
+    struct is_grayscale_image { const static bool value = pixel_traits<typename image_traits<image_type>::pixel_type>::grayscale; };
 
     // This is an optimized version of resize_image for the case where bilinear
     // interpolation is used.
@@ -535,17 +537,21 @@ namespace dlib
     typename disable_if_c<(is_rgb_image<image_type1>::value&&is_rgb_image<image_type2>::value) || 
                           (is_grayscale_image<image_type1>::value&&is_grayscale_image<image_type2>::value)>::type 
     resize_image (
-        const image_type1& in_img,
-        image_type2& out_img,
+        const image_type1& in_img_,
+        image_type2& out_img_,
         interpolate_bilinear
     )
     {
         // make sure requires clause is not broken
-        DLIB_ASSERT( is_same_object(in_img, out_img) == false ,
+        DLIB_ASSERT( is_same_object(in_img_, out_img_) == false ,
             "\t void resize_image()"
             << "\n\t Invalid inputs were given to this function."
-            << "\n\t is_same_object(in_img, out_img):  " << is_same_object(in_img, out_img)
+            << "\n\t is_same_object(in_img_, out_img_):  " << is_same_object(in_img_, out_img_)
             );
+
+        const_image_view<image_type1> in_img(in_img_);
+        image_view<image_type2> out_img(out_img_);
+
         if (out_img.nr() <= 1 || out_img.nc() <= 1)
         {
             assign_all_pixels(out_img, 0);
@@ -553,8 +559,8 @@ namespace dlib
         }
 
 
-        typedef typename image_type1::type T;
-        typedef typename image_type2::type U;
+        typedef typename image_traits<image_type1>::pixel_type T;
+        typedef typename image_traits<image_type2>::pixel_type U;
         const double x_scale = (in_img.nc()-1)/(double)std::max<long>((out_img.nc()-1),1);
         const double y_scale = (in_img.nr()-1)/(double)std::max<long>((out_img.nr()-1),1);
         double y = -y_scale;
@@ -618,24 +624,28 @@ namespace dlib
         typename image_type
         >
     typename enable_if<is_grayscale_image<image_type> >::type resize_image (
-        const image_type& in_img,
-        image_type& out_img,
+        const image_type& in_img_,
+        image_type& out_img_,
         interpolate_bilinear
     )
     {
         // make sure requires clause is not broken
-        DLIB_ASSERT( is_same_object(in_img, out_img) == false ,
+        DLIB_ASSERT( is_same_object(in_img_, out_img_) == false ,
             "\t void resize_image()"
             << "\n\t Invalid inputs were given to this function."
-            << "\n\t is_same_object(in_img, out_img):  " << is_same_object(in_img, out_img)
+            << "\n\t is_same_object(in_img_, out_img_):  " << is_same_object(in_img_, out_img_)
             );
+
+        const_image_view<image_type> in_img(in_img_);
+        image_view<image_type> out_img(out_img_);
+
         if (out_img.nr() <= 1 || out_img.nc() <= 1)
         {
             assign_all_pixels(out_img, 0);
             return;
         }
 
-        typedef typename image_type::type T;
+        typedef typename image_traits<image_type>::pixel_type T;
         const double x_scale = (in_img.nc()-1)/(double)std::max<long>((out_img.nc()-1),1);
         const double y_scale = (in_img.nr()-1)/(double)std::max<long>((out_img.nr()-1),1);
         double y = -y_scale;
@@ -716,17 +726,21 @@ namespace dlib
         typename image_type
         >
     typename enable_if<is_rgb_image<image_type> >::type resize_image (
-        const image_type& in_img,
-        image_type& out_img,
+        const image_type& in_img_,
+        image_type& out_img_,
         interpolate_bilinear
     )
     {
         // make sure requires clause is not broken
-        DLIB_ASSERT( is_same_object(in_img, out_img) == false ,
+        DLIB_ASSERT( is_same_object(in_img_, out_img_) == false ,
             "\t void resize_image()"
             << "\n\t Invalid inputs were given to this function."
-            << "\n\t is_same_object(in_img, out_img):  " << is_same_object(in_img, out_img)
+            << "\n\t is_same_object(in_img_, out_img_):  " << is_same_object(in_img_, out_img_)
             );
+
+        const_image_view<image_type> in_img(in_img_);
+        image_view<image_type> out_img(out_img_);
+
         if (out_img.nr() <= 1 || out_img.nc() <= 1)
         {
             assign_all_pixels(out_img, 0);
@@ -734,7 +748,7 @@ namespace dlib
         }
 
 
-        typedef typename image_type::type T;
+        typedef typename image_traits<image_type>::pixel_type T;
         const double x_scale = (in_img.nc()-1)/(double)std::max<long>((out_img.nc()-1),1);
         const double y_scale = (in_img.nr()-1)/(double)std::max<long>((out_img.nr()-1),1);
         double y = -y_scale;
@@ -1046,7 +1060,7 @@ namespace dlib
         for (unsigned long i = 0; i < images.size(); ++i)
         {
             flip_image_left_right(images[i], temp); 
-            temp.swap(images[i]);
+            swap(temp,images[i]);
             for (unsigned long j = 0; j < objects[i].size(); ++j)
             {
                 objects[i][j] = impl::flip_rect_left_right(objects[i][j], get_rect(images[i]));
@@ -1077,7 +1091,7 @@ namespace dlib
         for (unsigned long i = 0; i < images.size(); ++i)
         {
             flip_image_left_right(images[i], temp); 
-            temp.swap(images[i]);
+            swap(temp, images[i]);
             for (unsigned long j = 0; j < objects[i].size(); ++j)
             {
                 objects[i][j] = impl::flip_rect_left_right(objects[i][j], get_rect(images[i]));
@@ -1113,7 +1127,7 @@ namespace dlib
         for (unsigned long i = 0; i < images.size(); ++i)
         {
             pyramid_up(images[i], temp, pyr);
-            temp.swap(images[i]);
+            swap(temp, images[i]);
             for (unsigned long j = 0; j < objects[i].size(); ++j)
             {
                 objects[i][j] = pyr.rect_up(objects[i][j]);
@@ -1146,7 +1160,7 @@ namespace dlib
         for (unsigned long i = 0; i < images.size(); ++i)
         {
             pyramid_up(images[i], temp, pyr);
-            temp.swap(images[i]);
+            swap(temp, images[i]);
             for (unsigned long j = 0; j < objects[i].size(); ++j)
             {
                 objects[i][j] = pyr.rect_up(objects[i][j]);
@@ -1179,7 +1193,7 @@ namespace dlib
         for (unsigned long i = 0; i < images.size(); ++i)
         {
             const point_transform_affine tran = rotate_image(images[i], temp, angle);
-            temp.swap(images[i]);
+            swap(temp, images[i]);
             for (unsigned long j = 0; j < objects[i].size(); ++j)
             {
                 const rectangle rect = objects[i][j];
@@ -1210,7 +1224,7 @@ namespace dlib
         for (unsigned long i = 0; i < images.size(); ++i)
         {
             const point_transform_affine tran = rotate_image(images[i], temp, angle);
-            temp.swap(images[i]);
+            swap(temp, images[i]);
             for (unsigned long j = 0; j < objects[i].size(); ++j)
             {
                 const rectangle rect = objects[i][j];
@@ -1325,9 +1339,9 @@ namespace dlib
             << "\n\t is_same_object(in_img, out_img):  " << is_same_object(in_img, out_img)
             );
 
-        if (in_img.size() == 0)
+        if (image_size(in_img) == 0)
         {
-            out_img.clear();
+            set_image_size(out_img, 0, 0);
             return;
         }
 
@@ -1335,10 +1349,10 @@ namespace dlib
         rectangle uprect = pyr.rect_up(rect);
         if (uprect.is_empty())
         {
-            out_img.clear();
+            set_image_size(out_img, 0, 0);
             return;
         }
-        out_img.set_size(uprect.bottom()+1, uprect.right()+1);
+        set_image_size(out_img, uprect.bottom()+1, uprect.right()+1);
 
         resize_image(in_img, out_img, interp);
     }
@@ -1379,7 +1393,7 @@ namespace dlib
     {
         image_type temp;
         pyramid_up(img, temp, pyr);
-        temp.swap(img);
+        swap(temp, img);
     }
 
 // ----------------------------------------------------------------------------------------
@@ -1502,7 +1516,7 @@ namespace dlib
         chips.resize(chip_locations.size());
         for (unsigned long i = 0; i < chips.size(); ++i)
         {
-            chips[i].set_size(chip_locations[i].rows, chip_locations[i].cols);
+            set_image_size(chips[i], chip_locations[i].rows, chip_locations[i].cols);
 
             // figure out which level in the pyramid to use to extract the chip
             int level = -1;
@@ -1545,7 +1559,7 @@ namespace dlib
         std::vector<chip_details> chip_locations(1,location);
         dlib::array<image_type2> chips;
         extract_image_chips(img, chip_locations, chips);
-        chips[0].swap(chip);
+        swap(chips[0], chip);
     }
 
 // ----------------------------------------------------------------------------------------

dlib/image_transforms/interpolation_abstract.h

@@ -22,18 +22,18 @@ namespace dlib
     public:
 
         template <
-            typename image_type, 
+            typename image_view_type, 
             typename pixel_type
             >
         bool operator() (
-            const image_type& img,
+            const image_view_type& img,
             const dlib::point& p,
             pixel_type& result
         ) const;
         /*!
             requires
-                - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-                - pixel_traits<typename image_type::type>::has_alpha == false
+                - image_view_type == an image_view or const_image_view object. 
+                - pixel_traits<typename image_view_type::pixel_type>::has_alpha == false
                 - pixel_traits<pixel_type> is defined
             ensures
                 - if (p is located inside img) then
@@ -63,18 +63,18 @@ namespace dlib
 
         template <
             typename T, 
-            typename image_type,
+            typename image_view_type,
             typename pixel_type
             >
         bool operator() (
-            const image_type& img,
+            const image_view_type& img,
             const dlib::vector<T,2>& p,
             pixel_type& result
         ) const;
         /*!
             requires
-                - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-                - pixel_traits<typename image_type::type>::has_alpha == false
+                - image_view_type == an image_view or const_image_view object 
+                - pixel_traits<typename image_view_type::pixel_type>::has_alpha == false
                 - pixel_traits<pixel_type> is defined
             ensures
                 - if (there is an interpolatable image location at point p in img) then
@@ -104,18 +104,18 @@ namespace dlib
 
         template <
             typename T, 
-            typename image_type,
+            typename image_view_type,
             typename pixel_type
             >
         bool operator() (
-            const image_type& img,
+            const image_view_type& img,
             const dlib::vector<T,2>& p,
             pixel_type& result
         ) const;
         /*!
             requires
-                - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-                - pixel_traits<typename image_type::type>::has_alpha == false
+                - image_view_type == an image_view or const_image_view object. 
+                - pixel_traits<typename image_view_type::pixel_type>::has_alpha == false
                 - pixel_traits<pixel_type> is defined
             ensures
                 - if (there is an interpolatable image location at point p in img) then
@@ -197,15 +197,17 @@ namespace dlib
     );
     /*!
         requires
-            - image_type1 == is an implementation of array2d/array2d_kernel_abstract.h
-            - image_type2 == is an implementation of array2d/array2d_kernel_abstract.h
+            - image_type1 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - image_type2 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - interpolation_type == interpolate_nearest_neighbor, interpolate_bilinear, 
               interpolate_quadratic, or a type with a compatible interface.
             - map_point should be a function which takes dlib::vector<T,2> objects and
               returns dlib::vector<T,2> objects.  An example is point_transform_affine.
             - set_background should be a function which can take a single argument of
-              type image_type2::type.  Examples are black_background, white_background,
-              and no_background.
+              type image_traits<image_type2>::pixel_type.  Examples are black_background,
+              white_background, and no_background.
             - get_rect(out_img).contains(area) == true
             - is_same_object(in_img, out_img) == false
         ensures
@@ -241,14 +243,16 @@ namespace dlib
     );
     /*!
         requires
-            - image_type1 == is an implementation of array2d/array2d_kernel_abstract.h
-            - image_type2 == is an implementation of array2d/array2d_kernel_abstract.h
+            - image_type1 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - image_type2 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - interpolation_type == interpolate_nearest_neighbor, interpolate_bilinear, 
               interpolate_quadratic, or a type with a compatible interface.
             - map_point should be a function which takes dlib::vector<T,2> objects and
               returns dlib::vector<T,2> objects.  An example is point_transform_affine.
             - set_background should be a function which can take a single argument of
-              type image_type2::type.  Examples are black_background, white_background,
+              type image_traits<image_type2>::pixel_type.  Examples are black_background, white_background,
               and no_background.
             - is_same_object(in_img, out_img) == false
         ensures
@@ -273,8 +277,10 @@ namespace dlib
     );
     /*!
         requires
-            - image_type1 == is an implementation of array2d/array2d_kernel_abstract.h
-            - image_type2 == is an implementation of array2d/array2d_kernel_abstract.h
+            - image_type1 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - image_type2 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - interpolation_type == interpolate_nearest_neighbor, interpolate_bilinear, 
               interpolate_quadratic, or a type with a compatible interface.
             - map_point should be a function which takes dlib::vector<T,2> objects and
@@ -302,8 +308,10 @@ namespace dlib
     );
     /*!
         requires
-            - image_type1 == is an implementation of array2d/array2d_kernel_abstract.h
-            - image_type2 == is an implementation of array2d/array2d_kernel_abstract.h
+            - image_type1 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - image_type2 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - interpolation_type == interpolate_nearest_neighbor, interpolate_bilinear, 
               interpolate_quadratic, or a type with a compatible interface.
             - is_same_object(in_img, out_img) == false
@@ -331,10 +339,11 @@ namespace dlib
     );
     /*!
         requires
-            - image_type1 == is an implementation of array2d/array2d_kernel_abstract.h
-            - image_type2 == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type1::type>::has_alpha == false
-            - pixel_traits<typename image_type2::type> is defined
+            - image_type1 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - image_type2 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - pixel_traits<typename image_traits<image_type1>::pixel_type>::has_alpha == false
             - is_same_object(in_img, out_img) == false
         ensures
             - #out_img == a copy of in_img which has been rotated angle radians counter clockwise.
@@ -359,8 +368,10 @@ namespace dlib
     );
     /*!
         requires
-            - image_type1 == is an implementation of array2d/array2d_kernel_abstract.h
-            - image_type2 == is an implementation of array2d/array2d_kernel_abstract.h
+            - image_type1 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - image_type2 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - interpolation_type == interpolate_nearest_neighbor, interpolate_bilinear, 
               interpolate_quadratic, or a type with a compatible interface.
             - is_same_object(in_img, out_img) == false
@@ -387,10 +398,11 @@ namespace dlib
     );
     /*!
         requires
-            - image_type1 == is an implementation of array2d/array2d_kernel_abstract.h
-            - image_type2 == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type1::type>::has_alpha == false
-            - pixel_traits<typename image_type2::type> is defined
+            - image_type1 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - image_type2 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - pixel_traits<typename image_traits<image_type1>::pixel_type>::has_alpha == false
             - is_same_object(in_img, out_img) == false
         ensures
             - #out_img == A copy of in_img which has been stretched so that it 
@@ -413,10 +425,10 @@ namespace dlib
     );
     /*!
         requires
-            - image_type1 == is an implementation of array2d/array2d_kernel_abstract.h
-            - image_type2 == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type1::type> is defined
-            - pixel_traits<typename image_type2::type> is defined
+            - image_type1 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - image_type2 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - is_same_object(in_img, out_img) == false
         ensures
             - #out_img.nr() == in_img.nr()
@@ -439,8 +451,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type::type> is defined
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - T == rectangle or full_object_detection
             - images.size() == objects.size()
         ensures
@@ -470,8 +482,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type::type> is defined
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - images.size() == objects.size()
             - images.size() == objects2.size()
             - T == rectangle or full_object_detection
@@ -507,10 +519,10 @@ namespace dlib
     );
     /*!
         requires
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - is_vector(angles) == true
             - angles.size() > 0
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type::type> is defined
             - images.size() == objects.size()
             - images.size() == objects2.size()
             - T == rectangle or full_object_detection
@@ -545,10 +557,10 @@ namespace dlib
     );
     /*!
         requires
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - is_vector(angles) == true
             - angles.size() > 0
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type::type> is defined
             - images.size() == objects.size()
             - T == rectangle or full_object_detection
         ensures
@@ -567,8 +579,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type::type> is defined
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - images.size() == objects.size()
         ensures
             - This function replaces each image in images with the left/right flipped
@@ -593,8 +605,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type::type> is defined
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - images.size() == objects.size()
             - images.size() == objects2.size()
         ensures
@@ -623,8 +635,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type::type> is defined
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - images.size() == objects.size()
         ensures
             - This function replaces each image in images with an upsampled version of that
@@ -651,8 +663,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type::type> is defined
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - images.size() == objects.size()
             - images.size() == objects2.size()
         ensures
@@ -680,8 +692,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type::type> is defined
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - images.size() == objects.size()
         ensures
             - This function replaces each image in images with a rotated version of that
@@ -711,8 +723,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type::type> is defined
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - images.size() == objects.size()
             - images.size() == objects2.size()
         ensures
@@ -747,10 +759,10 @@ namespace dlib
     );
     /*!
         requires
-            - image_type1 == is an implementation of array2d/array2d_kernel_abstract.h
-            - image_type2 == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type1::type> is defined
-            - pixel_traits<typename image_type2::type> is defined
+            - image_type1 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - image_type2 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - is_same_object(in_img, out_img) == false
         ensures
             - #out_img.nr() == in_img.nr()
@@ -774,8 +786,10 @@ namespace dlib
     );
     /*!
         requires
-            - image_type1 == is an implementation of array2d/array2d_kernel_abstract.h
-            - image_type2 == is an implementation of array2d/array2d_kernel_abstract.h
+            - image_type1 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - image_type2 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - pyramid_type == a type compatible with the image pyramid objects defined 
               in dlib/image_transforms/image_pyramid_abstract.h
             - interpolation_type == interpolate_nearest_neighbor, interpolate_bilinear, 
@@ -810,8 +824,10 @@ namespace dlib
     );
     /*!
         requires
-            - image_type1 == is an implementation of array2d/array2d_kernel_abstract.h
-            - image_type2 == is an implementation of array2d/array2d_kernel_abstract.h
+            - image_type1 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - image_type2 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - pyramid_type == a type compatible with the image pyramid objects defined 
               in dlib/image_transforms/image_pyramid_abstract.h
             - is_same_object(in_img, out_img) == false
@@ -831,7 +847,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - pyramid_type == a type compatible with the image pyramid objects defined 
               in dlib/image_transforms/image_pyramid_abstract.h
         ensures
@@ -851,7 +868,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
         ensures
             - performs: pyramid_up(img, pyramid_down<2>());
               (i.e. it upsamples the given image and doubles it in size.)
@@ -998,10 +1016,11 @@ namespace dlib
     );
     /*!
         requires
-            - image_type1 == is an implementation of array2d/array2d_kernel_abstract.h
-            - image_type2 == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename image_type1::type>::has_alpha == false
-            - pixel_traits<typename image_type2::type> is defined
+            - image_type1 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - image_type2 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - pixel_traits<typename image_traits<image_type1>::pixel_type>::has_alpha == false
             - for all valid i: 
                 - chip_locations[i].rect.is_empty() == false
                 - chip_locations[i].size != 0

dlib/image_transforms/label_connected_blobs.h

@@ -113,19 +113,21 @@ namespace dlib
         typename connected_functor_type
         >
     unsigned long label_connected_blobs (
-        const image_type& img,
+        const image_type& img_,
         const background_functor_type& is_background,
         const neighbors_functor_type&  get_neighbors,
         const connected_functor_type&  is_connected,
-        label_image_type& label_img
+        label_image_type& label_img_
     )
     {
         // make sure requires clause is not broken
-        DLIB_ASSERT(is_same_object(img, label_img) == false,
+        DLIB_ASSERT(is_same_object(img_, label_img_) == false,
             "\t unsigned long label_connected_blobs()"
             << "\n\t The input image and output label image can't be the same object."
             );
 
+        const_image_view<image_type> img(img_);
+        image_view<label_image_type> label_img(label_img_);
 
         std::stack<point> neighbors;
         label_img.set_size(img.nr(), img.nc());

dlib/image_transforms/label_connected_blobs_abstract.h

@@ -58,9 +58,9 @@ namespace dlib
                 with the label_connected_blobs() routine defined below.
         !*/
 
-        template <typename image_type>
+        template <typename image_view_type>
         bool operator() (
-            const image_type& img,
+            const image_view_type& img,
             const point& a,
             const point& b
         ) const
@@ -77,9 +77,9 @@ namespace dlib
                 with the label_connected_blobs() routine defined below.
         !*/
 
-        template <typename image_type>
+        template <typename image_view_type>
         bool operator() (
-            const image_type& img,
+            const image_view_type& img,
             const point& a,
             const point& b
         ) const
@@ -98,9 +98,9 @@ namespace dlib
                 with the label_connected_blobs() routine defined below.
         !*/
 
-        template <typename image_type>
+        template <typename image_view_type>
         bool operator() (
-            const image_type& img,
+            const image_view_type& img,
             const point& p
         ) const
         {
@@ -117,9 +117,9 @@ namespace dlib
                 with the label_connected_blobs() routine defined below.
         !*/
 
-        template <typename image_type>
+        template <typename image_view_type>
         bool operator() (
-            const image_type&, 
+            const image_view_type&, 
             const point& 
         ) const
         {
@@ -146,9 +146,10 @@ namespace dlib
     );
     /*!
         requires
-            - image_type       == is an implementation of array2d/array2d_kernel_abstract.h
-            - label_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-              and it must contain integers.
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - label_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h and it must contain integer pixels.
             - is_background(img, point(c,r)) is a legal expression that evaluates to a bool.
             - is_connected(img, point(c,r), point(c2,r2)) is a legal expression that
               evaluates to a bool.

dlib/image_transforms/morphological_operations.h

@@ -16,14 +16,15 @@ namespace dlib
     {
         template <typename image_type>
         bool is_binary_image (
-            const image_type& img
+            const image_type& img_
         )
         /*!
             ensures
-                - returns true if img contains only on_pixel and off_pixel values.
+                - returns true if img_ contains only on_pixel and off_pixel values.
                 - returns false otherwise
         !*/
         {
+            const_image_view<image_type> img(img_);
             for (long r = 0; r < img.nr(); ++r)
             {
                 for (long c = 0; c < img.nc(); ++c)
@@ -75,23 +76,25 @@ namespace dlib
         long N
         >
     void binary_dilation (
-        const in_image_type& in_img,
-        out_image_type& out_img,
+        const in_image_type& in_img_,
+        out_image_type& out_img_,
         const unsigned char (&structuring_element)[M][N]
     )
     {
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+        typedef typename image_traits<in_image_type>::pixel_type in_pixel_type;
+        typedef typename image_traits<out_image_type>::pixel_type out_pixel_type;
+        COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<out_pixel_type>::has_alpha == false );
 
         using namespace morphological_operations_helpers;
         COMPILE_TIME_ASSERT(M%2 == 1);
         COMPILE_TIME_ASSERT(N%2 == 1);
-        DLIB_ASSERT(is_same_object(in_img,out_img) == false,
+        DLIB_ASSERT(is_same_object(in_img_,out_img_) == false,
             "\tvoid binary_dilation()"
             << "\n\tYou must give two different image objects"
             );
-        COMPILE_TIME_ASSERT(pixel_traits<typename in_image_type::type>::grayscale);
-        DLIB_ASSERT(is_binary_image(in_img) ,
+        COMPILE_TIME_ASSERT(pixel_traits<in_pixel_type>::grayscale);
+        DLIB_ASSERT(is_binary_image(in_img_) ,
             "\tvoid binary_dilation()"
             << "\n\tin_img must be a binary image"
             );
@@ -101,6 +104,8 @@ namespace dlib
             );
 
 
+        const_image_view<in_image_type> in_img(in_img_);
+        image_view<out_image_type> out_img(out_img_);
 
         // if there isn't any input image then don't do anything
         if (in_img.size() == 0)
@@ -147,23 +152,25 @@ namespace dlib
         long N
         >
     void binary_erosion (
-        const in_image_type& in_img,
-        out_image_type& out_img,
+        const in_image_type& in_img_,
+        out_image_type& out_img_,
         const unsigned char (&structuring_element)[M][N]
     )
     {
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+        typedef typename image_traits<in_image_type>::pixel_type in_pixel_type;
+        typedef typename image_traits<out_image_type>::pixel_type out_pixel_type;
+        COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<out_pixel_type>::has_alpha == false );
 
         using namespace morphological_operations_helpers;
         COMPILE_TIME_ASSERT(M%2 == 1);
         COMPILE_TIME_ASSERT(N%2 == 1);
-        DLIB_ASSERT(is_same_object(in_img,out_img) == false,
+        DLIB_ASSERT(is_same_object(in_img_,out_img_) == false,
             "\tvoid binary_erosion()"
             << "\n\tYou must give two different image objects"
             );
-        COMPILE_TIME_ASSERT(pixel_traits<typename in_image_type::type>::grayscale);
-        DLIB_ASSERT(is_binary_image(in_img) ,
+        COMPILE_TIME_ASSERT(pixel_traits<in_pixel_type>::grayscale);
+        DLIB_ASSERT(is_binary_image(in_img_) ,
             "\tvoid binary_erosion()"
             << "\n\tin_img must be a binary image"
             );
@@ -172,6 +179,8 @@ namespace dlib
             << "\n\tthe structuring_element must be a binary image"
             );
 
+        const_image_view<in_image_type> in_img(in_img_);
+        image_view<out_image_type> out_img(out_img_);
 
 
         // if there isn't any input image then don't do anything
@@ -229,8 +238,10 @@ namespace dlib
         const unsigned long iter = 1
     )
     {
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+        typedef typename image_traits<in_image_type>::pixel_type in_pixel_type;
+        typedef typename image_traits<out_image_type>::pixel_type out_pixel_type;
+        COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<out_pixel_type>::has_alpha == false );
 
         using namespace morphological_operations_helpers;
         COMPILE_TIME_ASSERT(M%2 == 1);
@@ -239,7 +250,7 @@ namespace dlib
             "\tvoid binary_open()"
             << "\n\tYou must give two different image objects"
             );
-        COMPILE_TIME_ASSERT(pixel_traits<typename in_image_type::type>::grayscale);
+        COMPILE_TIME_ASSERT(pixel_traits<in_pixel_type>::grayscale);
         DLIB_ASSERT(is_binary_image(in_img) ,
             "\tvoid binary_open()"
             << "\n\tin_img must be a binary image"
@@ -251,13 +262,13 @@ namespace dlib
 
 
         // if there isn't any input image then don't do anything
-        if (in_img.size() == 0)
+        if (num_rows(in_img)*num_columns(in_img) == 0)
         {
-            out_img.clear();
+            set_image_size(out_img, 0,0);
             return;
         }
 
-        out_img.set_size(in_img.nr(),in_img.nc());
+        set_image_size(out_img, num_rows(in_img), num_columns(in_img));
 
         if (iter == 0)
         {
@@ -278,14 +289,14 @@ namespace dlib
             // do the extra erosions
             for (unsigned long i = 1; i < iter; ++i)
             {
-                temp1.swap(temp2);
+                swap(temp1, temp2);
                 binary_erosion(temp2,temp1,structuring_element);
             }
 
             // do the extra dilations 
             for (unsigned long i = 1; i < iter; ++i)
             {
-                temp1.swap(temp2);
+                swap(temp1, temp2);
                 binary_dilation(temp2,temp1,structuring_element);
             }
 
@@ -308,8 +319,11 @@ namespace dlib
         const unsigned long iter = 1
     )
     {
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+        typedef typename image_traits<in_image_type>::pixel_type in_pixel_type;
+        typedef typename image_traits<out_image_type>::pixel_type out_pixel_type;
+        COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<out_pixel_type>::has_alpha == false );
+
 
         using namespace morphological_operations_helpers;
         COMPILE_TIME_ASSERT(M%2 == 1);
@@ -318,7 +332,7 @@ namespace dlib
             "\tvoid binary_close()"
             << "\n\tYou must give two different image objects"
             );
-        COMPILE_TIME_ASSERT(pixel_traits<typename in_image_type::type>::grayscale);
+        COMPILE_TIME_ASSERT(pixel_traits<in_pixel_type>::grayscale);
         DLIB_ASSERT(is_binary_image(in_img) ,
             "\tvoid binary_close()"
             << "\n\tin_img must be a binary image"
@@ -330,13 +344,13 @@ namespace dlib
 
 
         // if there isn't any input image then don't do anything
-        if (in_img.size() == 0)
+        if (num_rows(in_img)*num_columns(in_img) == 0)
         {
-            out_img.clear();
+            set_image_size(out_img, 0,0);
             return;
         }
 
-        out_img.set_size(in_img.nr(),in_img.nc());
+        set_image_size(out_img, num_rows(in_img), num_columns(in_img));
 
         if (iter == 0)
         {
@@ -357,14 +371,14 @@ namespace dlib
             // do the extra dilations 
             for (unsigned long i = 1; i < iter; ++i)
             {
-                temp1.swap(temp2);
+                swap(temp1, temp2);
                 binary_dilation(temp2,temp1,structuring_element);
             }
 
             // do the extra erosions 
             for (unsigned long i = 1; i < iter; ++i)
             {
-                temp1.swap(temp2);
+                swap(temp1, temp2);
                 binary_erosion(temp2,temp1,structuring_element);
             }
 
@@ -380,26 +394,34 @@ namespace dlib
         typename out_image_type
         >
     void binary_intersection (
-        const in_image_type1& in_img1,
-        const in_image_type2& in_img2,
-        out_image_type& out_img
+        const in_image_type1& in_img1_,
+        const in_image_type2& in_img2_,
+        out_image_type& out_img_
     )
     {
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type1::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type2::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+        typedef typename image_traits<in_image_type1>::pixel_type in_pixel_type1;
+        typedef typename image_traits<in_image_type2>::pixel_type in_pixel_type2;
+        typedef typename image_traits<out_image_type>::pixel_type out_pixel_type;
+        COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type1>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type2>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<out_pixel_type>::has_alpha == false );
 
         using namespace morphological_operations_helpers;
-        COMPILE_TIME_ASSERT(pixel_traits<typename in_image_type1::type>::grayscale);
-        COMPILE_TIME_ASSERT(pixel_traits<typename in_image_type2::type>::grayscale);
-        DLIB_ASSERT(is_binary_image(in_img1) ,
+        COMPILE_TIME_ASSERT(pixel_traits<in_pixel_type1>::grayscale);
+        COMPILE_TIME_ASSERT(pixel_traits<in_pixel_type2>::grayscale);
+        DLIB_ASSERT(is_binary_image(in_img1_) ,
             "\tvoid binary_intersection()"
             << "\n\tin_img1 must be a binary image"
             );
-        DLIB_ASSERT(is_binary_image(in_img2) ,
+        DLIB_ASSERT(is_binary_image(in_img2_) ,
             "\tvoid binary_intersection()"
             << "\n\tin_img2 must be a binary image"
             );
+
+        const_image_view<in_image_type1> in_img1(in_img1_);
+        const_image_view<in_image_type2> in_img2(in_img2_);
+        image_view<out_image_type> out_img(out_img_);
+
         DLIB_ASSERT(in_img1.nc() == in_img2.nc(),
             "\tvoid binary_intersection()"
             << "\n\tin_img1 and in_img2 must have the same ncs."
@@ -444,26 +466,35 @@ namespace dlib
         typename out_image_type
         >
     void binary_union (
-        const in_image_type1& in_img1,
-        const in_image_type2& in_img2,
-        out_image_type& out_img
+        const in_image_type1& in_img1_,
+        const in_image_type2& in_img2_,
+        out_image_type& out_img_
     )
     {
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type1::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type2::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+        typedef typename image_traits<in_image_type1>::pixel_type in_pixel_type1;
+        typedef typename image_traits<in_image_type2>::pixel_type in_pixel_type2;
+        typedef typename image_traits<out_image_type>::pixel_type out_pixel_type;
+        COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type1>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type2>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<out_pixel_type>::has_alpha == false );
+
 
         using namespace morphological_operations_helpers;
-        COMPILE_TIME_ASSERT(pixel_traits<typename in_image_type1::type>::grayscale);
-        COMPILE_TIME_ASSERT(pixel_traits<typename in_image_type2::type>::grayscale);
-        DLIB_ASSERT(is_binary_image(in_img1) ,
+        COMPILE_TIME_ASSERT(pixel_traits<in_pixel_type1>::grayscale);
+        COMPILE_TIME_ASSERT(pixel_traits<in_pixel_type2>::grayscale);
+        DLIB_ASSERT(is_binary_image(in_img1_) ,
             "\tvoid binary_intersection()"
             << "\n\tin_img1 must be a binary image"
             );
-        DLIB_ASSERT(is_binary_image(in_img2) ,
+        DLIB_ASSERT(is_binary_image(in_img2_) ,
             "\tvoid binary_intersection()"
             << "\n\tin_img2 must be a binary image"
             );
+
+        const_image_view<in_image_type1> in_img1(in_img1_);
+        const_image_view<in_image_type2> in_img2(in_img2_);
+        image_view<out_image_type> out_img(out_img_);
+
         DLIB_ASSERT(in_img1.nc() == in_img2.nc(),
             "\tvoid binary_intersection()"
             << "\n\tin_img1 and in_img2 must have the same ncs."
@@ -508,26 +539,34 @@ namespace dlib
         typename out_image_type
         >
     void binary_difference (
-        const in_image_type1& in_img1,
-        const in_image_type2& in_img2,
-        out_image_type& out_img
+        const in_image_type1& in_img1_,
+        const in_image_type2& in_img2_,
+        out_image_type& out_img_
     )
     {
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type1::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type2::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+        typedef typename image_traits<in_image_type1>::pixel_type in_pixel_type1;
+        typedef typename image_traits<in_image_type2>::pixel_type in_pixel_type2;
+        typedef typename image_traits<out_image_type>::pixel_type out_pixel_type;
+        COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type1>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type2>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<out_pixel_type>::has_alpha == false );
 
         using namespace morphological_operations_helpers;
-        COMPILE_TIME_ASSERT(pixel_traits<typename in_image_type1::type>::grayscale);
-        COMPILE_TIME_ASSERT(pixel_traits<typename in_image_type2::type>::grayscale);
-        DLIB_ASSERT(is_binary_image(in_img1) ,
+        COMPILE_TIME_ASSERT(pixel_traits<in_pixel_type1>::grayscale);
+        COMPILE_TIME_ASSERT(pixel_traits<in_pixel_type2>::grayscale);
+        DLIB_ASSERT(is_binary_image(in_img1_) ,
             "\tvoid binary_difference()"
             << "\n\tin_img1 must be a binary image"
             );
-        DLIB_ASSERT(is_binary_image(in_img2) ,
+        DLIB_ASSERT(is_binary_image(in_img2_) ,
             "\tvoid binary_difference()"
             << "\n\tin_img2 must be a binary image"
             );
+
+        const_image_view<in_image_type1> in_img1(in_img1_);
+        const_image_view<in_image_type2> in_img2(in_img2_);
+        image_view<out_image_type> out_img(out_img_);
+
         DLIB_ASSERT(in_img1.nc() == in_img2.nc(),
             "\tvoid binary_difference()"
             << "\n\tin_img1 and in_img2 must have the same ncs."
@@ -571,20 +610,25 @@ namespace dlib
         typename out_image_type
         >
     void binary_complement (
-        const in_image_type& in_img,
-        out_image_type& out_img
+        const in_image_type& in_img_,
+        out_image_type& out_img_
     )
     {
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+        typedef typename image_traits<in_image_type>::pixel_type in_pixel_type;
+        typedef typename image_traits<out_image_type>::pixel_type out_pixel_type;
+        COMPILE_TIME_ASSERT( pixel_traits<in_pixel_type>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<out_pixel_type>::has_alpha == false );
+
 
         using namespace morphological_operations_helpers;
-        COMPILE_TIME_ASSERT(pixel_traits<typename in_image_type::type>::grayscale);
-        DLIB_ASSERT(is_binary_image(in_img) ,
+        COMPILE_TIME_ASSERT(pixel_traits<in_pixel_type>::grayscale);
+        DLIB_ASSERT(is_binary_image(in_img_) ,
             "\tvoid binary_complement()"
             << "\n\tin_img must be a binary image"
             );
 
+        const_image_view<in_image_type> in_img(in_img_);
+        image_view<out_image_type> out_img(out_img_);
 
         // if there isn't any input image then don't do anything
         if (in_img.size() == 0)

dlib/image_transforms/morphological_operations_abstract.h

@@ -24,11 +24,11 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename in_image_type::type>::grayscale == true   
-            - pixel_traits<typename in_image_type::type>::has_alpha == false
-            - pixel_traits<typename out_image_type::type>::has_alpha == false 
+            - in_image_type and out_image_type are image objects that implement the
+              interface defined in dlib/image_processing/generic_image.h 
+            - in_img must contain a grayscale pixel type.
+            - both in_img and out_img must contain pixels with no alpha channel.
+              (i.e. pixel_traits::has_alpha==false for their pixels)
             - is_same_object(in_img,out_img) == false
             - M % 2 == 1  (i.e. M must be odd)
             - N % 2 == 1  (i.e. N must be odd)
@@ -58,11 +58,11 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename in_image_type::type>::grayscale == true   
-            - pixel_traits<typename in_image_type::type>::has_alpha == false
-            - pixel_traits<typename out_image_type::type>::has_alpha == false 
+            - in_image_type and out_image_type are image objects that implement the
+              interface defined in dlib/image_processing/generic_image.h 
+            - in_img must contain a grayscale pixel type.
+            - both in_img and out_img must contain pixels with no alpha channel.
+              (i.e. pixel_traits::has_alpha==false for their pixels)
             - is_same_object(in_img,out_img) == false
             - M % 2 == 1  (i.e. M must be odd)
             - N % 2 == 1  (i.e. N must be odd)
@@ -93,11 +93,11 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename in_image_type::type>::grayscale == true   
-            - pixel_traits<typename in_image_type::type>::has_alpha == false
-            - pixel_traits<typename out_image_type::type>::has_alpha == false 
+            - in_image_type and out_image_type are image objects that implement the
+              interface defined in dlib/image_processing/generic_image.h 
+            - in_img must contain a grayscale pixel type.
+            - both in_img and out_img must contain pixels with no alpha channel.
+              (i.e. pixel_traits::has_alpha==false for their pixels)
             - is_same_object(in_img,out_img) == false
             - M % 2 == 1  (i.e. M must be odd)
             - N % 2 == 1  (i.e. N must be odd)
@@ -129,11 +129,11 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename in_image_type::type>::grayscale == true   
-            - pixel_traits<typename in_image_type::type>::has_alpha == false
-            - pixel_traits<typename out_image_type::type>::has_alpha == false 
+            - in_image_type and out_image_type are image objects that implement the
+              interface defined in dlib/image_processing/generic_image.h 
+            - in_img must contain a grayscale pixel type.
+            - both in_img and out_img must contain pixels with no alpha channel.
+              (i.e. pixel_traits::has_alpha==false for their pixels)
             - is_same_object(in_img,out_img) == false
             - M % 2 == 1  (i.e. M must be odd)
             - N % 2 == 1  (i.e. N must be odd)
@@ -163,14 +163,11 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type1 == is an implementation of array2d/array2d_kernel_abstract.h
-            - in_image_type2 == is an implementation of array2d/array2d_kernel_abstract.h
-            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename in_image_type1::type>::grayscale == true   
-            - pixel_traits<typename in_image_type2::type>::grayscale == true   
-            - pixel_traits<typename in_image_type1::type>::has_alpha == false
-            - pixel_traits<typename in_image_type2::type>::has_alpha == false
-            - pixel_traits<typename out_image_type::type>::has_alpha == false 
+            - in_image_type1, in_image_type2, and out_image_type are image objects that
+              implement the interface defined in dlib/image_processing/generic_image.h 
+            - in_img1 and in_img2 must contain grayscale pixel types.
+            - in_img1, in_img2, and out_img must contain pixels with no alpha channel.
+              (i.e. pixel_traits::has_alpha==false for their pixels)
             - all pixels in in_img1 and in_img2 are set to either on_pixel or off_pixel
               (i.e. they must be binary images)
             - in_img1.nc() == in_img2.nc()
@@ -197,14 +194,11 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type1 == is an implementation of array2d/array2d_kernel_abstract.h
-            - in_image_type2 == is an implementation of array2d/array2d_kernel_abstract.h
-            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename in_image_type1::type>::grayscale == true   
-            - pixel_traits<typename in_image_type2::type>::grayscale == true   
-            - pixel_traits<typename in_image_type1::type>::has_alpha == false
-            - pixel_traits<typename in_image_type2::type>::has_alpha == false
-            - pixel_traits<typename out_image_type::type>::has_alpha == false 
+            - in_image_type1, in_image_type2, and out_image_type are image objects that
+              implement the interface defined in dlib/image_processing/generic_image.h 
+            - in_img1 and in_img2 must contain grayscale pixel types.
+            - in_img1, in_img2, and out_img must contain pixels with no alpha channel.
+              (i.e. pixel_traits::has_alpha==false for their pixels)
             - all pixels in in_img1 and in_img2 are set to either on_pixel or off_pixel
               (i.e. they must be binary images)
             - in_img1.nc() == in_img2.nc()
@@ -231,14 +225,11 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type1 == is an implementation of array2d/array2d_kernel_abstract.h
-            - in_image_type2 == is an implementation of array2d/array2d_kernel_abstract.h
-            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename in_image_type1::type>::grayscale == true   
-            - pixel_traits<typename in_image_type2::type>::grayscale == true   
-            - pixel_traits<typename in_image_type1::type>::has_alpha == false
-            - pixel_traits<typename in_image_type2::type>::has_alpha == false
-            - pixel_traits<typename out_image_type::type>::has_alpha == false 
+            - in_image_type1, in_image_type2, and out_image_type are image objects that
+              implement the interface defined in dlib/image_processing/generic_image.h 
+            - in_img1 and in_img2 must contain grayscale pixel types.
+            - in_img1, in_img2, and out_img must contain pixels with no alpha channel.
+              (i.e. pixel_traits::has_alpha==false for their pixels)
             - all pixels in in_img1 and in_img2 are set to either on_pixel or off_pixel
               (i.e. they must be binary images)
             - in_img1.nc() == in_img2.nc()
@@ -263,11 +254,11 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename in_image_type::type>::grayscale == true   
-            - pixel_traits<typename in_image_type::type>::has_alpha == false
-            - pixel_traits<typename out_image_type::type>::has_alpha == false 
+            - in_image_type and out_image_type are image objects that implement the
+              interface defined in dlib/image_processing/generic_image.h 
+            - in_img must contain a grayscale pixel type.
+            - both in_img and out_img must contain pixels with no alpha channel.
+              (i.e. pixel_traits::has_alpha==false for their pixels)
             - all pixels in in_img are set to either on_pixel or off_pixel
               (i.e. it must be a binary image)
         ensures

dlib/image_transforms/segment_image.h

@@ -125,18 +125,28 @@ namespace dlib
 
     // ------------------------------------------------------------------------------------
 
+        namespace impl
+        {
+            template <typename image_view_type>
+            struct uint8_or_uint16_pixels
+            {
+                typedef typename image_view_type::pixel_type pixel_type;
+                const static bool value = is_same_type<pixel_type,uint8>::value ||
+                                          is_same_type<pixel_type,uint16>::value;
+            };
+        }
+
         // This is an overload of get_pixel_edges() that is optimized to segment images
         // with 8bit or 16bit  pixels very quickly.  We do this by using a radix sort
         // instead of quicksort.
         template <typename in_image_type, typename T>
-        typename enable_if_c<is_same_type<typename in_image_type::type,uint8>::value ||
-                             is_same_type<typename in_image_type::type,uint16>::value>::type 
+        typename enable_if<impl::uint8_or_uint16_pixels<in_image_type> >::type 
         get_pixel_edges (
             const in_image_type& in_img,
             std::vector<segment_image_edge_data_T<T> >& sorted_edges
         )
         {
-            typedef typename in_image_type::type ptype;
+            typedef typename in_image_type::pixel_type ptype;
             typedef T diff_type;
             std::vector<unsigned long> counts(std::numeric_limits<ptype>::max()+1, 0);
 
@@ -243,8 +253,7 @@ namespace dlib
 
         // This is the general purpose version of get_pixel_edges().  It handles all pixel types.
         template <typename in_image_type, typename T>
-        typename disable_if_c<is_same_type<typename in_image_type::type,uint8>::value ||
-                              is_same_type<typename in_image_type::type,uint16>::value>::type 
+        typename disable_if<impl::uint8_or_uint16_pixels<in_image_type> >::type 
         get_pixel_edges (
             const in_image_type& in_img,
             std::vector<segment_image_edge_data_T<T> >& sorted_edges
@@ -253,7 +262,7 @@ namespace dlib
             const rectangle area = get_rect(in_img);
             sorted_edges.reserve(area.area()*4);
 
-            typedef typename in_image_type::type ptype;
+            typedef typename in_image_type::pixel_type ptype;
             edge_diff_funct<ptype> edge_diff;
             typedef T diff_type;
             typedef segment_image_edge_data_T<T> segment_image_edge_data;
@@ -327,23 +336,26 @@ namespace dlib
         typename out_image_type
         >
     void segment_image (
-        const in_image_type& in_img,
-        out_image_type& out_img,
+        const in_image_type& in_img_,
+        out_image_type& out_img_,
         const double k = 200,
         const unsigned long min_size = 10
     )
     {
         using namespace dlib::impl;
-        typedef typename in_image_type::type ptype;
+        typedef typename image_traits<in_image_type>::pixel_type ptype;
         typedef typename edge_diff_funct<ptype>::diff_type diff_type;
 
         // make sure requires clause is not broken
-        DLIB_ASSERT(is_same_object(in_img, out_img) == false,
+        DLIB_ASSERT(is_same_object(in_img_, out_img_) == false,
             "\t void segment_image()"
             << "\n\t The input images can't be the same object."
             );
 
-        COMPILE_TIME_ASSERT(is_unsigned_type<typename out_image_type::type>::value);
+        COMPILE_TIME_ASSERT(is_unsigned_type<typename image_traits<out_image_type>::pixel_type>::value);
+
+        const_image_view<in_image_type> in_img(in_img_);
+        image_view<out_image_type> out_img(out_img_);
 
         out_img.set_size(in_img.nr(), in_img.nc());
         // don't bother doing anything if the image is too small
@@ -610,7 +622,7 @@ namespace dlib
         typename EXP
         >
     void find_candidate_object_locations (
-        const in_image_type& in_img,
+        const in_image_type& in_img_,
         std::vector<rectangle>& rects,
         const matrix_exp<EXP>& kvals,
         const unsigned long min_size = 20,
@@ -629,9 +641,10 @@ namespace dlib
         typedef dlib::set<rectangle, mm_type>::kernel_1a set_of_rects;
 
         using namespace dlib::impl;
-        typedef typename in_image_type::type ptype;
+        typedef typename image_traits<in_image_type>::pixel_type ptype;
         typedef typename edge_diff_funct<ptype>::diff_type diff_type;
 
+        const_image_view<in_image_type> in_img(in_img_);
 
         // don't bother doing anything if the image is too small
         if (in_img.nr() < 2 || in_img.nc() < 2)

dlib/image_transforms/segment_image_abstract.h

@@ -23,11 +23,13 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type  == an implementation of array2d/array2d_kernel_abstract.h
-            - out_image_type == an implementation of array2d/array2d_kernel_abstract.h
-            - in_image_type::type  == Any pixel type with a pixel_traits specialization or a
-              dlib matrix object representing a row or column vector.
-            - out_image_type::type == unsigned integer type 
+            - in_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - out_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - in_image_type can contain any pixel type with a pixel_traits specialization
+              or a dlib matrix object representing a row or column vector.
+            - out_image_type must contain an unsigned integer pixel type.
             - is_same_object(in_img, out_img) == false
         ensures
             - Attempts to segment in_img into regions which have some visual consistency to
@@ -65,6 +67,8 @@ namespace dlib
     );
     /*!
         requires
+            - in_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - is_vector(kvals) == true
             - kvals.size() > 0
         ensures

dlib/image_transforms/spatial_filtering.h

@@ -27,17 +27,17 @@ namespace dlib
             typename T
             >
         rectangle grayscale_spatially_filter_image (
-            const in_image_type& in_img,
-            out_image_type& out_img,
-            const matrix_exp<EXP>& _filter,
+            const in_image_type& in_img_,
+            out_image_type& out_img_,
+            const matrix_exp<EXP>& filter_,
             T scale,
             bool use_abs,
             bool add_to
         )
         {
-            const_temp_matrix<EXP> filter(_filter);
-            COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-            COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+            const_temp_matrix<EXP> filter(filter_);
+            COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<in_image_type>::pixel_type>::has_alpha == false );
+            COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<out_image_type>::pixel_type>::has_alpha == false );
 
             DLIB_ASSERT(scale != 0 && filter.size() != 0,
                 "\trectangle spatially_filter_image()"
@@ -46,12 +46,14 @@ namespace dlib
                 << "\n\t filter.nr(): "<< filter.nr()
                 << "\n\t filter.nc(): "<< filter.nc()
             );
-            DLIB_ASSERT(is_same_object(in_img, out_img) == false,
+            DLIB_ASSERT(is_same_object(in_img_, out_img_) == false,
                 "\trectangle spatially_filter_image()"
                 << "\n\tYou must give two different image objects"
             );
 
 
+            const_image_view<in_image_type> in_img(in_img_);
+            image_view<out_image_type> out_img(out_img_);
 
             // if there isn't any input image then don't do anything
             if (in_img.size() == 0)
@@ -71,7 +73,7 @@ namespace dlib
 
             const rectangle non_border = rectangle(first_col, first_row, last_col-1, last_row-1);
             if (!add_to)
-                zero_border_pixels(out_img, non_border); 
+                zero_border_pixels(out_img_, non_border); 
 
             // apply the filter to the image
             for (long r = first_row; r < last_row; ++r)
@@ -121,26 +123,28 @@ namespace dlib
             typename EXP
             >
         rectangle float_spatially_filter_image (
-            const in_image_type& in_img,
-            out_image_type& out_img,
-            const matrix_exp<EXP>& _filter,
+            const in_image_type& in_img_,
+            out_image_type& out_img_,
+            const matrix_exp<EXP>& filter_,
             bool add_to
         )
         {
 
-            const_temp_matrix<EXP> filter(_filter);
+            const_temp_matrix<EXP> filter(filter_);
             DLIB_ASSERT(filter.size() != 0,
                 "\trectangle spatially_filter_image()"
                 << "\n\t You can't give an empty filter."
                 << "\n\t filter.nr(): "<< filter.nr()
                 << "\n\t filter.nc(): "<< filter.nc()
             );
-            DLIB_ASSERT(is_same_object(in_img, out_img) == false,
+            DLIB_ASSERT(is_same_object(in_img_, out_img_) == false,
                 "\trectangle spatially_filter_image()"
                 << "\n\tYou must give two different image objects"
             );
 
 
+            const_image_view<in_image_type> in_img(in_img_);
+            image_view<out_image_type> out_img(out_img_);
 
             // if there isn't any input image then don't do anything
             if (in_img.size() == 0)
@@ -160,7 +164,7 @@ namespace dlib
 
             const rectangle non_border = rectangle(first_col, first_row, last_col-1, last_row-1);
             if (!add_to)
-                zero_border_pixels(out_img, non_border); 
+                zero_border_pixels(out_img_, non_border); 
 
             // apply the filter to the image
             for (long r = first_row; r < last_row; ++r)
@@ -243,8 +247,8 @@ namespace dlib
         >
     struct is_float_filtering2
     {
-        const static bool value = is_same_type<typename in_image_type::type,float>::value &&
-                                  is_same_type<typename out_image_type::type,float>::value &&
+        const static bool value = is_same_type<typename image_traits<in_image_type>::pixel_type,float>::value &&
+                                  is_same_type<typename image_traits<out_image_type>::pixel_type,float>::value &&
                                   is_same_type<typename EXP::type,float>::value;
     };
 
@@ -256,7 +260,7 @@ namespace dlib
         typename EXP,
         typename T
         >
-    typename enable_if_c<pixel_traits<typename out_image_type::type>::grayscale && 
+    typename enable_if_c<pixel_traits<typename image_traits<out_image_type>::pixel_type>::grayscale && 
                          is_float_filtering2<in_image_type,out_image_type,EXP>::value,rectangle>::type 
     spatially_filter_image (
         const in_image_type& in_img,
@@ -288,7 +292,7 @@ namespace dlib
         typename EXP,
         typename T
         >
-    typename enable_if_c<pixel_traits<typename out_image_type::type>::grayscale && 
+    typename enable_if_c<pixel_traits<typename image_traits<out_image_type>::pixel_type>::grayscale && 
                          !is_float_filtering2<in_image_type,out_image_type,EXP>::value,rectangle>::type 
     spatially_filter_image (
         const in_image_type& in_img,
@@ -310,17 +314,17 @@ namespace dlib
         typename EXP,
         typename T
         >
-    typename disable_if_c<pixel_traits<typename out_image_type::type>::grayscale,rectangle>::type 
+    typename disable_if_c<pixel_traits<typename image_traits<out_image_type>::pixel_type>::grayscale,rectangle>::type 
     spatially_filter_image (
-        const in_image_type& in_img,
-        out_image_type& out_img,
-        const matrix_exp<EXP>& _filter,
+        const in_image_type& in_img_,
+        out_image_type& out_img_,
+        const matrix_exp<EXP>& filter_,
         T scale
     )
     {
-        const_temp_matrix<EXP> filter(_filter);
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+        const_temp_matrix<EXP> filter(filter_);
+        COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<in_image_type>::pixel_type>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<out_image_type>::pixel_type>::has_alpha == false );
 
         DLIB_ASSERT(scale != 0 && filter.size() != 0,
             "\trectangle spatially_filter_image()"
@@ -329,12 +333,14 @@ namespace dlib
             << "\n\t filter.nr(): "<< filter.nr()
             << "\n\t filter.nc(): "<< filter.nc()
             );
-        DLIB_ASSERT(is_same_object(in_img, out_img) == false,
+        DLIB_ASSERT(is_same_object(in_img_, out_img_) == false,
             "\trectangle spatially_filter_image()"
             << "\n\tYou must give two different image objects"
             );
 
 
+        const_image_view<in_image_type> in_img(in_img_);
+        image_view<out_image_type> out_img(out_img_);
 
         // if there isn't any input image then don't do anything
         if (in_img.size() == 0)
@@ -360,7 +366,8 @@ namespace dlib
         {
             for (long c = first_col; c < last_col; ++c)
             {
-                typedef matrix<typename EXP::type,pixel_traits<typename in_image_type::type>::num,1> ptype;
+                typedef typename image_traits<in_image_type>::pixel_type pixel_type;
+                typedef matrix<typename EXP::type,pixel_traits<pixel_type>::num,1> ptype;
                 ptype p;
                 ptype temp;
                 temp = 0;
@@ -376,7 +383,7 @@ namespace dlib
 
                 temp /= scale;
 
-                typename in_image_type::type pp;
+                pixel_type pp;
                 vector_to_pixel(pp, temp);
                 assign_pixel(out_img[r][c], pp);
             }
@@ -415,8 +422,8 @@ namespace dlib
             typename T
             >
         rectangle grayscale_spatially_filter_image_separable (
-            const in_image_type& in_img,
-            out_image_type& out_img,
+            const in_image_type& in_img_,
+            out_image_type& out_img_,
             const matrix_exp<EXP1>& _row_filter,
             const matrix_exp<EXP2>& _col_filter,
             T scale,
@@ -426,8 +433,8 @@ namespace dlib
         {
             const_temp_matrix<EXP1> row_filter(_row_filter);
             const_temp_matrix<EXP2> col_filter(_col_filter);
-            COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-            COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+            COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<in_image_type>::pixel_type>::has_alpha == false );
+            COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<out_image_type>::pixel_type>::has_alpha == false );
 
             DLIB_ASSERT(scale != 0 && row_filter.size() != 0 && col_filter.size() != 0 &&
                 is_vector(row_filter) &&
@@ -440,12 +447,14 @@ namespace dlib
                 << "\n\t is_vector(row_filter): "<< is_vector(row_filter)
                 << "\n\t is_vector(col_filter): "<< is_vector(col_filter)
             );
-            DLIB_ASSERT(is_same_object(in_img, out_img) == false,
+            DLIB_ASSERT(is_same_object(in_img_, out_img_) == false,
                 "\trectangle spatially_filter_image_separable()"
                 << "\n\tYou must give two different image objects"
             );
 
 
+            const_image_view<in_image_type> in_img(in_img_);
+            image_view<out_image_type> out_img(out_img_);
 
             // if there isn't any input image then don't do anything
             if (in_img.size() == 0)
@@ -467,10 +476,9 @@ namespace dlib
             if (!add_to)
                 zero_border_pixels(out_img, non_border); 
 
-            typedef typename out_image_type::mem_manager_type mem_manager_type;
             typedef typename EXP1::type ptype;
 
-            array2d<ptype,mem_manager_type> temp_img;
+            array2d<ptype> temp_img;
             temp_img.set_size(in_img.nr(), in_img.nc());
 
             // apply the row filter
@@ -534,8 +542,8 @@ namespace dlib
         >
     struct is_float_filtering
     {
-        const static bool value = is_same_type<typename in_image_type::type,float>::value &&
-                                  is_same_type<typename out_image_type::type,float>::value &&
+        const static bool value = is_same_type<typename image_traits<in_image_type>::pixel_type,float>::value &&
+                                  is_same_type<typename image_traits<out_image_type>::pixel_type,float>::value &&
                                   is_same_type<typename EXP1::type,float>::value &&
                                   is_same_type<typename EXP2::type,float>::value;
     };
@@ -551,11 +559,11 @@ namespace dlib
         typename EXP2
         >
     rectangle float_spatially_filter_image_separable (
-        const in_image_type& in_img,
-        out_image_type& out_img,
+        const in_image_type& in_img_,
+        out_image_type& out_img_,
         const matrix_exp<EXP1>& _row_filter,
         const matrix_exp<EXP2>& _col_filter,
-        out_image_type& scratch,
+        out_image_type& scratch_,
         bool add_to = false
     )
     {
@@ -576,12 +584,14 @@ namespace dlib
             << "\n\t is_vector(row_filter): "<< is_vector(row_filter)
             << "\n\t is_vector(col_filter): "<< is_vector(col_filter)
         );
-        DLIB_ASSERT(is_same_object(in_img, out_img) == false,
+        DLIB_ASSERT(is_same_object(in_img_, out_img_) == false,
             "\trectangle float_spatially_filter_image_separable()"
             << "\n\tYou must give two different image objects"
         );
 
 
+        const_image_view<in_image_type> in_img(in_img_);
+        image_view<out_image_type> out_img(out_img_);
 
         // if there isn't any input image then don't do anything
         if (in_img.size() == 0)
@@ -602,6 +612,7 @@ namespace dlib
         if (!add_to)
             zero_border_pixels(out_img, non_border); 
 
+        image_view<out_image_type> scratch(scratch_);
         scratch.set_size(in_img.nr(), in_img.nc());
 
         // apply the row filter
@@ -712,7 +723,7 @@ namespace dlib
         typename EXP2,
         typename T
         >
-    typename enable_if_c<pixel_traits<typename out_image_type::type>::grayscale && 
+    typename enable_if_c<pixel_traits<typename image_traits<out_image_type>::pixel_type>::grayscale && 
                          is_float_filtering<in_image_type,out_image_type,EXP1,EXP2>::value,rectangle>::type 
     spatially_filter_image_separable (
         const in_image_type& in_img,
@@ -747,7 +758,7 @@ namespace dlib
         typename EXP2,
         typename T
         >
-    typename enable_if_c<pixel_traits<typename out_image_type::type>::grayscale && 
+    typename enable_if_c<pixel_traits<typename image_traits<out_image_type>::pixel_type>::grayscale && 
                          !is_float_filtering<in_image_type,out_image_type,EXP1,EXP2>::value,rectangle>::type 
     spatially_filter_image_separable (
         const in_image_type& in_img,
@@ -771,10 +782,10 @@ namespace dlib
         typename EXP2,
         typename T
         >
-    typename disable_if_c<pixel_traits<typename out_image_type::type>::grayscale,rectangle>::type 
+    typename disable_if_c<pixel_traits<typename image_traits<out_image_type>::pixel_type>::grayscale,rectangle>::type 
     spatially_filter_image_separable (
-        const in_image_type& in_img,
-        out_image_type& out_img,
+        const in_image_type& in_img_,
+        out_image_type& out_img_,
         const matrix_exp<EXP1>& _row_filter,
         const matrix_exp<EXP2>& _col_filter,
         T scale
@@ -782,8 +793,8 @@ namespace dlib
     {
         const_temp_matrix<EXP1> row_filter(_row_filter);
         const_temp_matrix<EXP2> col_filter(_col_filter);
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<in_image_type>::pixel_type>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<out_image_type>::pixel_type>::has_alpha == false );
 
         DLIB_ASSERT(scale != 0 && row_filter.size() != 0 && col_filter.size() != 0 &&
                     is_vector(row_filter) &&
@@ -796,12 +807,14 @@ namespace dlib
             << "\n\t is_vector(row_filter): "<< is_vector(row_filter)
             << "\n\t is_vector(col_filter): "<< is_vector(col_filter)
             );
-        DLIB_ASSERT(is_same_object(in_img, out_img) == false,
+        DLIB_ASSERT(is_same_object(in_img_, out_img_) == false,
             "\trectangle spatially_filter_image_separable()"
             << "\n\tYou must give two different image objects"
             );
 
 
+        const_image_view<in_image_type> in_img(in_img_);
+        image_view<out_image_type> out_img(out_img_);
 
         // if there isn't any input image then don't do anything
         if (in_img.size() == 0)
@@ -822,10 +835,10 @@ namespace dlib
         const rectangle non_border = rectangle(first_col, first_row, last_col-1, last_row-1);
         zero_border_pixels(out_img, non_border); 
 
-        typedef typename out_image_type::mem_manager_type mem_manager_type;
-        typedef matrix<typename EXP1::type,pixel_traits<typename in_image_type::type>::num,1> ptype;
+        typedef typename image_traits<in_image_type>::pixel_type pixel_type;
+        typedef matrix<typename EXP1::type,pixel_traits<pixel_type>::num,1> ptype;
 
-        array2d<ptype,mem_manager_type> temp_img;
+        array2d<ptype> temp_img;
         temp_img.set_size(in_img.nr(), in_img.nc());
 
         // apply the row filter
@@ -862,7 +875,7 @@ namespace dlib
 
 
                 // save this pixel to the output image
-                typename in_image_type::type p;
+                pixel_type p;
                 vector_to_pixel(p, temp);
                 assign_pixel(out_img[r][c], p);
             }
@@ -901,8 +914,8 @@ namespace dlib
         >
     rectangle spatially_filter_image_separable_down (
         const unsigned long downsample,
-        const in_image_type& in_img,
-        out_image_type& out_img,
+        const in_image_type& in_img_,
+        out_image_type& out_img_,
         const matrix_exp<EXP1>& row_filter,
         const matrix_exp<EXP2>& col_filter,
         T scale,
@@ -910,9 +923,9 @@ namespace dlib
         bool add_to = false
     )
     {
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::grayscale == true );
+        COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<in_image_type>::pixel_type>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<out_image_type>::pixel_type>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<out_image_type>::pixel_type>::grayscale == true );
 
         DLIB_ASSERT(downsample > 0 &&
                     scale != 0 &&
@@ -929,12 +942,14 @@ namespace dlib
             << "\n\t is_vector(row_filter): "<< is_vector(row_filter)
             << "\n\t is_vector(col_filter): "<< is_vector(col_filter)
             );
-        DLIB_ASSERT(is_same_object(in_img, out_img) == false,
+        DLIB_ASSERT(is_same_object(in_img_, out_img_) == false,
             "\trectangle spatially_filter_image_separable_down()"
             << "\n\tYou must give two different image objects"
             );
 
 
+        const_image_view<in_image_type> in_img(in_img_);
+        image_view<out_image_type> out_img(out_img_);
 
         // if there isn't any input image then don't do anything
         if (in_img.size() == 0)
@@ -961,8 +976,7 @@ namespace dlib
 
         typedef typename EXP1::type ptype;
 
-        typedef typename out_image_type::mem_manager_type mem_manager_type;
-        array2d<ptype,mem_manager_type> temp_img;
+        array2d<ptype> temp_img;
         temp_img.set_size(in_img.nr(), out_img.nc());
 
         // apply the row filter
@@ -1043,7 +1057,7 @@ namespace dlib
         >
     inline void separable_3x3_filter_block_grayscale (
         T (&block)[NR][NC],
-        const in_image_type& img,
+        const in_image_type& img_,
         const long& r,
         const long& c,
         const U& fe1, // separable filter end
@@ -1051,6 +1065,7 @@ namespace dlib
         const U& fe2 // separable filter end 2
     ) 
     {
+        const_image_view<in_image_type> img(img_);
         // make sure requires clause is not broken
         DLIB_ASSERT(shrink_rect(get_rect(img),1).contains(c,r) &&
                     shrink_rect(get_rect(img),1).contains(c+NC-1,r+NR-1),
@@ -1096,7 +1111,7 @@ namespace dlib
         >
     inline void separable_3x3_filter_block_rgb (
         T (&block)[NR][NC],
-        const in_image_type& img,
+        const in_image_type& img_,
         const long& r,
         const long& c,
         const U& fe1, // separable filter end
@@ -1104,6 +1119,7 @@ namespace dlib
         const U& fe2  // separable filter end 2
     ) 
     {
+        const_image_view<in_image_type> img(img_);
         // make sure requires clause is not broken
         DLIB_ASSERT(shrink_rect(get_rect(img),1).contains(c,r) &&
                     shrink_rect(get_rect(img),1).contains(c+NC-1,r+NR-1),
@@ -1217,7 +1233,7 @@ namespace dlib
             << "\n\t is_same_object(in_img,out_img): " << is_same_object(in_img,out_img) 
         );
 
-        typedef typename pixel_traits<typename out_image_type::type>::basic_pixel_type type;
+        typedef typename pixel_traits<typename image_traits<out_image_type>::pixel_type>::basic_pixel_type type;
         typedef typename promote<type>::type ptype;
 
         const matrix<ptype,0,1>& filt = create_gaussian_filter<ptype>(sigma, max_size);
@@ -1239,24 +1255,26 @@ namespace dlib
         typename image_type2
         >
     void sum_filter (
-        const image_type1& img,
-        image_type2& out,
+        const image_type1& img_,
+        image_type2& out_,
         const rectangle& rect
     )
     {
+        const_image_view<image_type1> img(img_);
+        image_view<image_type2> out(out_);
         DLIB_ASSERT(img.nr() == out.nr() &&
                     img.nc() == out.nc() &&
-                    is_same_object(img,out) == false,
+                    is_same_object(img_,out_) == false,
             "\t void sum_filter()"
             << "\n\t Invalid arguments given to this function."
             << "\n\t img.nr(): " << img.nr() 
             << "\n\t img.nc(): " << img.nc() 
             << "\n\t out.nr(): " << out.nr() 
             << "\n\t out.nc(): " << out.nc() 
-            << "\n\t is_same_object(img,out): " << is_same_object(img,out) 
+            << "\n\t is_same_object(img_,out_): " << is_same_object(img_,out_) 
         );
 
-        typedef typename image_type1::type pixel_type;
+        typedef typename image_traits<image_type1>::pixel_type pixel_type;
         typedef typename promote<pixel_type>::type ptype;
 
         std::vector<ptype> column_sum;
@@ -1324,9 +1342,9 @@ namespace dlib
                 cur_sum = cur_sum + column_sum[c+width] - column_sum[c];
 
                 if (add_to)
-                    out[r][c] += static_cast<typename image_type2::type>(cur_sum);
+                    out[r][c] += static_cast<typename image_traits<image_type2>::pixel_type>(cur_sum);
                 else
-                    out[r][c] = static_cast<typename image_type2::type>(cur_sum);
+                    out[r][c] = static_cast<typename image_traits<image_type2>::pixel_type>(cur_sum);
             }
         }
     }
@@ -1355,7 +1373,7 @@ namespace dlib
         const rectangle& rect
     )
     {
-        out.set_size(img.nr(), img.nc());
+        set_image_size(out, num_rows(img), num_columns(img));
         impl::sum_filter<false>(img,out,rect);
     }
 
@@ -1446,18 +1464,20 @@ namespace dlib
         typename image_type2
         >
     void max_filter (
-        image_type1& img,
-        image_type2& out,
+        image_type1& img_,
+        image_type2& out_,
         const long width,
         const long height,
-        const typename image_type1::type& thresh
+        const typename image_traits<image_type1>::pixel_type& thresh
     )
     {
+        image_view<image_type1> img(img_);
+        image_view<image_type2> out(out_);
         DLIB_ASSERT( width > 0 &&
                      height > 0 &&
                      out.nr() == img.nr() &&
                      out.nc() == img.nc() &&
-                     is_same_object(img,out) == false,
+                     is_same_object(img_,out_) == false,
                 "\t void max_filter()"
                 << "\n\t Invalid arguments given to this function."
                 << "\n\t img.nr(): " << img.nr() 
@@ -1466,10 +1486,10 @@ namespace dlib
                 << "\n\t out.nc(): " << out.nc() 
                 << "\n\t width:    " << width 
                 << "\n\t height:   " << height 
-                << "\n\t is_same_object(img,out): " << is_same_object(img,out) 
+                << "\n\t is_same_object(img_,out_): " << is_same_object(img_,out_) 
                      );
 
-        typedef typename image_type1::type pixel_type;
+        typedef typename image_traits<image_type1>::pixel_type pixel_type;
 
 
         dlib::impl::fast_deque<std::pair<long,pixel_type> > Q(std::max(width,height));

dlib/image_transforms/spatial_filtering_abstract.h

@@ -27,15 +27,17 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename in_image_type::type>::has_alpha == false
-            - pixel_traits<typename out_image_type::type>::has_alpha == false 
+            - in_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - out_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - in_img and out_img do not contain pixels with an alpha channel.  That is,
+              pixel_traits::has_alpha is false for the pixels in these objects.
             - is_same_object(in_img, out_img) == false 
             - T must be some scalar type
             - filter.size() != 0
             - scale != 0
-            - if (pixel_traits<typename in_image_type::type>::grayscale == false) then
+            - if (in_img doesn't contain grayscale pixels) then
                 - use_abs == false && add_to == false
                   (i.e. You can only use the use_abs and add_to options with grayscale images)
         ensures
@@ -47,7 +49,7 @@ namespace dlib
               any applicable color space conversion or value saturation is performed.  Note that if 
               add_to is true then the filtered output value will be added to out_img rather than 
               overwriting the original value.
-            - if (pixel_traits<typename in_image_type::type>::grayscale == false) then
+            - if (in_img doesn't contain grayscale pixels) then
                 - The filter is applied to each color channel independently.
             - if (use_abs == true) then
                 - pixel values after filtering that are < 0 are converted to their absolute values.
@@ -88,10 +90,12 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename in_image_type::type>::has_alpha == false
-            - pixel_traits<typename out_image_type::type>::has_alpha == false 
+            - in_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - out_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - in_img and out_img do not contain pixels with an alpha channel.  That is,
+              pixel_traits::has_alpha is false for the pixels in these objects.
             - is_same_object(in_img, out_img) == false 
             - T must be some scalar type
             - scale != 0
@@ -99,7 +103,7 @@ namespace dlib
             - col_filter.size() != 0
             - is_vector(row_filter) == true
             - is_vector(col_filter) == true
-            - if (pixel_traits<typename in_image_type::type>::grayscale == false) then
+            - if (in_img doesn't contain grayscale pixels) then
                 - use_abs == false && add_to == false
                   (i.e. You can only use the use_abs and add_to options with grayscale images)
         ensures
@@ -114,7 +118,7 @@ namespace dlib
               any applicable color space conversion or value saturation is performed.  Note that if 
               add_to is true then the filtered output value will be added to out_img rather than 
               overwriting the original value.
-            - if (pixel_traits<typename in_image_type::type>::grayscale == false) then
+            - if (in_img doesn't contain grayscale pixels) then
                 - The filter is applied to each color channel independently.
             - if (use_abs == true) then
                 - pixel values after filtering that are < 0 are converted to their absolute values
@@ -153,8 +157,10 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
+            - in_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - out_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - in_img, out_img, row_filter, and col_filter must all contain float type elements.
             - is_same_object(in_img, out_img) == false 
             - row_filter.size() != 0
@@ -196,11 +202,13 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename in_image_type::type>::has_alpha == false
-            - pixel_traits<typename out_image_type::type>::has_alpha == false 
-            - pixel_traits<typename out_image_type::type>::grayscale == true 
+            - in_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - out_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - in_img and out_img do not contain pixels with an alpha channel.  That is,
+              pixel_traits::has_alpha is false for the pixels in these objects.
+            - out_img contains grayscale pixels.
             - is_same_object(in_img, out_img) == false 
             - T must be some scalar type
             - scale != 0
@@ -244,8 +252,8 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename in_image_type::type> must be defined 
+            - in_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
             - T and U should be scalar types
             - shrink_rect(get_rect(img),1).contains(c,r)
             - shrink_rect(get_rect(img),1).contains(c+NC-1,r+NR-1)
@@ -281,8 +289,10 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename in_image_type::type>::rgb == true
+            - in_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - img must contain RGB pixels, that is pixel_traits::rgb == true for the pixels
+              in img.
             - T should be a struct with .red .green and .blue members.
             - U should be a scalar type
             - shrink_rect(get_rect(img),1).contains(c,r)
@@ -350,10 +360,12 @@ namespace dlib
     );
     /*!
         requires
-            - in_image_type  == is an implementation of array2d/array2d_kernel_abstract.h
-            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename in_image_type::type>::has_alpha == false
-            - pixel_traits<typename out_image_type::type>::has_alpha == false 
+            - in_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - out_image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - in_img and out_img do not contain pixels with an alpha channel.  That is,
+              pixel_traits::has_alpha is false for the pixels in these objects.
             - is_same_object(in_img, out_img) == false 
             - sigma > 0
             - max_size > 0
@@ -365,7 +377,7 @@ namespace dlib
               results are stored into #out_img.
             - Pixel values are stored into out_img using the assign_pixel() function and therefore
               any applicable color space conversion or value saturation is performed.
-            - if (pixel_traits<typename in_image_type::type>::grayscale == false) then
+            - if (in_img doesn't contain grayscale pixels) then
                 - The filter is applied to each color channel independently.
             - Pixels close enough to the edge of in_img to not have the filter still fit 
               inside the image are set to zero.
@@ -388,10 +400,10 @@ namespace dlib
         requires
             - out.nr() == img.nr() 
             - out.nc() == img.nc()
-            - image_type1 == an implementation of array2d/array2d_kernel_abstract.h
-              and it must contain a scalar type
-            - image_type2 == an implementation of array2d/array2d_kernel_abstract.h
-              and it must contain a scalar type
+            - image_type1 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h and it must contain grayscale pixels.
+            - image_type2 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h and it must contain grayscale pixels.
             - is_same_object(img,out) == false
         ensures
             - for all valid r and c:
@@ -413,10 +425,10 @@ namespace dlib
     );
     /*!
         requires
-            - image_type1 == an implementation of array2d/array2d_kernel_abstract.h
-              and it must contain a scalar type
-            - image_type2 == an implementation of array2d/array2d_kernel_abstract.h
-              and it must contain a scalar type
+            - image_type1 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h and it must contain grayscale pixels.
+            - image_type2 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h and it must contain grayscale pixels.
             - is_same_object(img,out) == false
         ensures
             - #out.nr() == img.nr() 
@@ -438,16 +450,16 @@ namespace dlib
         image_type2& out,
         const long width,
         const long height,
-        const typename image_type1::type& thresh
+        const typename image_traits<image_type1>::pixel_type& thresh
     );
     /*!
         requires
             - out.nr() == img.nr() 
             - out.nc() == img.nc()
-            - image_type1 == an implementation of array2d/array2d_kernel_abstract.h
-              and it must contain a scalar type
-            - image_type2 == an implementation of array2d/array2d_kernel_abstract.h
-              and it must contain a scalar type
+            - image_type1 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h and it must contain grayscale pixels.
+            - image_type2 == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h and it must contain grayscale pixels.
             - is_same_object(img,out) == false
             - width > 0 && height > 0
         ensures

dlib/image_transforms/thresholding.h

@@ -22,15 +22,18 @@ namespace dlib
         typename out_image_type
         >
     void threshold_image (
-        const in_image_type& in_img,
-        out_image_type& out_img,
-        typename pixel_traits<typename in_image_type::type>::basic_pixel_type thresh
+        const in_image_type& in_img_,
+        out_image_type& out_img_,
+        typename pixel_traits<typename image_traits<in_image_type>::pixel_type>::basic_pixel_type thresh
     )
     {
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<in_image_type>::pixel_type>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<out_image_type>::pixel_type>::has_alpha == false );
 
-        COMPILE_TIME_ASSERT(pixel_traits<typename out_image_type::type>::grayscale);
+        COMPILE_TIME_ASSERT(pixel_traits<typename image_traits<out_image_type>::pixel_type>::grayscale);
+
+        const_image_view<in_image_type> in_img(in_img_);
+        image_view<out_image_type> out_img(out_img_);
 
         // if there isn't any input image then don't do anything
         if (in_img.size() == 0)
@@ -60,7 +63,7 @@ namespace dlib
         >
     void threshold_image (
         image_type& img,
-        typename pixel_traits<typename image_type::type>::basic_pixel_type thresh
+        typename pixel_traits<typename image_traits<image_type>::pixel_type>::basic_pixel_type thresh
     )
     {
         threshold_image(img,img,thresh);
@@ -73,16 +76,19 @@ namespace dlib
         typename out_image_type
         >
     void auto_threshold_image (
-        const in_image_type& in_img,
-        out_image_type& out_img
+        const in_image_type& in_img_,
+        out_image_type& out_img_
     )
     {
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::is_unsigned == true );
-        COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::is_unsigned == true );
+        COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<in_image_type>::pixel_type>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<out_image_type>::pixel_type>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<in_image_type>::pixel_type>::is_unsigned == true );
+        COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<out_image_type>::pixel_type>::is_unsigned == true );
+
+        COMPILE_TIME_ASSERT(pixel_traits<typename image_traits<out_image_type>::pixel_type>::grayscale);
 
-        COMPILE_TIME_ASSERT(pixel_traits<typename out_image_type::type>::grayscale);
+        const_image_view<in_image_type> in_img(in_img_);
+        image_view<out_image_type> out_img(out_img_);
 
         // if there isn't any input image then don't do anything
         if (in_img.size() == 0)
@@ -171,7 +177,7 @@ namespace dlib
         thresh = (a + b)/2;
 
         // now actually apply the threshold
-        threshold_image(in_img,out_img,thresh);
+        threshold_image(in_img_,out_img_,thresh);
     }
 
     template <
@@ -191,25 +197,28 @@ namespace dlib
         typename out_image_type
         >
     void hysteresis_threshold (
-        const in_image_type& in_img,
-        out_image_type& out_img,
-        typename pixel_traits<typename in_image_type::type>::basic_pixel_type lower_thresh,
-        typename pixel_traits<typename in_image_type::type>::basic_pixel_type upper_thresh
+        const in_image_type& in_img_,
+        out_image_type& out_img_,
+        typename pixel_traits<typename image_traits<in_image_type>::pixel_type>::basic_pixel_type lower_thresh,
+        typename pixel_traits<typename image_traits<in_image_type>::pixel_type>::basic_pixel_type upper_thresh
     )
     {
-        COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
-        COMPILE_TIME_ASSERT( pixel_traits<typename out_image_type::type>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<in_image_type>::pixel_type>::has_alpha == false );
+        COMPILE_TIME_ASSERT( pixel_traits<typename image_traits<out_image_type>::pixel_type>::has_alpha == false );
 
-        COMPILE_TIME_ASSERT(pixel_traits<typename out_image_type::type>::grayscale);
+        COMPILE_TIME_ASSERT(pixel_traits<typename image_traits<out_image_type>::pixel_type>::grayscale);
 
-        DLIB_ASSERT( lower_thresh <= upper_thresh && is_same_object(in_img, out_img) == false,
-            "\tvoid hysteresis_threshold(in_img, out_img, lower_thresh, upper_thresh)"
+        DLIB_ASSERT( lower_thresh <= upper_thresh && is_same_object(in_img_, out_img_) == false,
+            "\tvoid hysteresis_threshold(in_img_, out_img_, lower_thresh, upper_thresh)"
             << "\n\tYou can't use an upper_thresh that is less than your lower_thresh"
             << "\n\tlower_thresh: " << lower_thresh 
             << "\n\tupper_thresh: " << upper_thresh 
-            << "\n\tis_same_object(in_img,out_img): " << is_same_object(in_img,out_img) 
+            << "\n\tis_same_object(in_img_,out_img_): " << is_same_object(in_img_,out_img_) 
             );
 
+        const_image_view<in_image_type> in_img(in_img_);
+        image_view<out_image_type> out_img(out_img_);
+
         // if there isn't any input image then don't do anything
         if (in_img.size() == 0)
         {
@@ -229,7 +238,7 @@ namespace dlib
         {
             for (long c = 0; c < in_img.nc(); ++c)
             {
-                typename pixel_traits<typename in_image_type::type>::basic_pixel_type p;
+                typename pixel_traits<typename image_traits<in_image_type>::pixel_type>::basic_pixel_type p;
                 assign_pixel(p,in_img[r][c]);
                 if (p >= upper_thresh)
                 {

dlib/image_transforms/thresholding_abstract.h

@@ -22,15 +22,15 @@ namespace dlib
     void threshold_image (
         const in_image_type& in_img,
         out_image_type& out_img,
-        typename pixel_traits<typename in_image_type::type>::basic_pixel_type thresh
+        typename pixel_traits<typename image_traits<in_image_type>::pixel_type>::basic_pixel_type thresh
     );
     /*!
         requires
             - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
             - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename out_image_type::type>::grayscale == true  
-            - pixel_traits<typename in_image_type::type>::has_alpha == false
-            - pixel_traits<typename out_image_type::type>::has_alpha == false 
+            - pixel_traits<typename image_traits<out_image_type>::pixel_type>::grayscale == true  
+            - pixel_traits<typename image_traits<in_image_type>::pixel_type>::has_alpha == false
+            - pixel_traits<typename image_traits<out_image_type>::pixel_type>::has_alpha == false 
         ensures
             - #out_img == the thresholded version of in_img (in_img is converted to a grayscale
               intensity image if it is color).  Pixels in in_img with grayscale values >= thresh 
@@ -44,7 +44,7 @@ namespace dlib
         >
     void threshold_image (
         image_type& img,
-        typename pixel_traits<typename image_type::type>::basic_pixel_type thresh
+        typename pixel_traits<typename image_traits<image_type>::pixel_type>::basic_pixel_type thresh
     );
     /*!
         requires
@@ -67,12 +67,12 @@ namespace dlib
         requires
             - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
             - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename in_image_type::type>::max() <= 65535 
-            - pixel_traits<typename in_image_type::type>::has_alpha   == false
-            - pixel_traits<typename in_image_type::type>::is_unsigned == true 
-            - pixel_traits<typename out_image_type::type>::grayscale  == true  
-            - pixel_traits<typename out_image_type::type>::has_alpha  == false 
-            - pixel_traits<typename out_image_type::type>::is_unsigned == true 
+            - pixel_traits<typename image_traits<in_image_type>::pixel_type>::max() <= 65535 
+            - pixel_traits<typename image_traits<in_image_type>::pixel_type>::has_alpha   == false
+            - pixel_traits<typename image_traits<in_image_type>::pixel_type>::is_unsigned == true 
+            - pixel_traits<typename image_traits<out_image_type>::pixel_type>::grayscale  == true  
+            - pixel_traits<typename image_traits<out_image_type>::pixel_type>::has_alpha  == false 
+            - pixel_traits<typename image_traits<out_image_type>::pixel_type>::is_unsigned == true 
         ensures
             - #out_img == the thresholded version of in_img (in_img is converted to a grayscale
               intensity image if it is color).  Pixels in in_img with grayscale values >= thresh 
@@ -106,16 +106,16 @@ namespace dlib
     void hysteresis_threshold (
         const in_image_type& in_img,
         out_image_type& out_img,
-        typename pixel_traits<typename in_image_type::type>::basic_pixel_type lower_thresh,
-        typename pixel_traits<typename in_image_type::type>::basic_pixel_type upper_thresh
+        typename pixel_traits<typename image_traits<in_image_type>::pixel_type>::basic_pixel_type lower_thresh,
+        typename pixel_traits<typename image_traits<in_image_type>::pixel_type>::basic_pixel_type upper_thresh
     );
     /*!
         requires
             - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
             - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
-            - pixel_traits<typename out_image_type::type>::grayscale == true  
-            - pixel_traits<typename in_image_type::type>::has_alpha == false
-            - pixel_traits<typename out_image_type::type>::has_alpha == false 
+            - pixel_traits<typename image_traits<out_image_type>::pixel_type>::grayscale == true  
+            - pixel_traits<typename image_traits<in_image_type>::pixel_type>::has_alpha == false
+            - pixel_traits<typename image_traits<out_image_type>::pixel_type>::has_alpha == false 
             - lower_thresh <= upper_thresh
             - is_same_object(in_img, out_img) == false
         ensures

dlib/matrix.h

@@ -13,6 +13,7 @@
 #include "matrix/matrix_conv.h"
 #include "matrix/matrix_read_from_istream.h"
 #include "matrix/matrix_fft.h"
+#include "matrix/matrix_generic_image.h"
 
 #ifdef DLIB_USE_BLAS
 #include "matrix/matrix_blas_bindings.h"

dlib/matrix/matrix_generic_image.h

+// Copyright (C) 2014  Davis E. King (davis@dlib.net)
+// License: Boost Software License   See LICENSE.txt for the full license.
+#ifndef DLIB_MATRIX_GENERIC_iMAGE_H__
+#define DLIB_MATRIX_GENERIC_iMAGE_H__
+
+#include "matrix.h"
+#include "../image_processing/generic_image.h"
+
+namespace dlib
+{
+    template <
+        typename T,
+        long NR,
+        long NC,
+        typename MM
+        >
+    struct image_traits<matrix<T,NR,NC,MM> >
+    {
+        typedef T pixel_type;
+    };
+
+    template <
+        typename T,
+        long NR,
+        long NC,
+        typename MM
+        >
+    inline long num_rows( const matrix<T,NR,NC,MM>& img) { return img.nr(); }
+
+    template <
+        typename T,
+        long NR,
+        long NC,
+        typename MM
+        >
+    inline long num_columns( const matrix<T,NR,NC,MM>& img) { return img.nc(); }
+
+    template <
+        typename T,
+        long NR,
+        long NC,
+        typename MM
+        >
+    inline void set_image_size(
+        matrix<T,NR,NC,MM>& img,
+        long rows,
+        long cols 
+    ) { img.set_size(rows,cols); }
+
+    template <
+        typename T,
+        long NR,
+        long NC,
+        typename MM
+        >
+    inline void* image_data(
+        matrix<T,NR,NC,MM>& img
+    )
+    {
+        if (img.size() != 0)
+            return &img(0,0);
+        else
+            return 0;
+    }
+
+    template <
+        typename T,
+        long NR,
+        long NC,
+        typename MM
+        >
+    inline const void* image_data(
+        const matrix<T,NR,NC,MM>& img
+    )
+    {
+        if (img.size() != 0)
+            return &img(0,0);
+        else
+            return 0;
+    }
+
+    template <
+        typename T,
+        long NR,
+        long NC,
+        typename MM
+        >
+    inline long width_step(
+        const matrix<T,NR,NC,MM>& img
+    ) 
+    { 
+        return img.nc()*sizeof(T);
+    }
+
+}
+
+#endif // DLIB_MATRIX_GENERIC_iMAGE_H__
+
+

dlib/matrix/matrix_mat.h

@@ -9,6 +9,7 @@
 #include "matrix_op.h"
 #include "../array2d.h"
 #include "../array.h"
+#include "../image_processing/generic_image.h"
 
 
 namespace dlib
@@ -28,39 +29,112 @@ namespace dlib
 
 // ----------------------------------------------------------------------------------------
 
-    template <typename T>
-    struct op_array2d_to_mat : does_not_alias 
+    template <typename image_type, typename pixel_type>
+    struct op_image_to_mat : does_not_alias 
     {
-        op_array2d_to_mat( const T& array_) : array(array_){}
+        op_image_to_mat( const image_type& img) : imgview(img){}
 
-        const T& array;
+        const_image_view<image_type> imgview;
 
         const static long cost = 1;
         const static long NR = 0;
         const static long NC = 0;
-        typedef typename T::type type;
-        typedef const typename T::type& const_ret_type;
-        typedef typename T::mem_manager_type mem_manager_type;
+        typedef pixel_type type;
+        typedef const pixel_type& const_ret_type;
+        typedef default_memory_manager mem_manager_type;
         typedef row_major_layout layout_type;
 
-        const_ret_type apply (long r, long c ) const { return array[r][c]; }
+        const_ret_type apply (long r, long c ) const { return imgview[r][c]; }
 
-        long nr () const { return array.nr(); }
-        long nc () const { return array.nc(); }
+        long nr () const { return imgview.nr(); }
+        long nc () const { return imgview.nc(); }
     }; 
 
 // ----------------------------------------------------------------------------------------
 
     template <
-        typename T,
-        typename MM
-        >
-    const matrix_op<op_array2d_to_mat<array2d<T,MM> > > mat (
-        const array2d<T,MM>& array
+        typename image_type
+        > // The reason we disable this if it is a matrix is because this matrix_op claims
+          // to not alias any matrix.  But obviously that would be a problem if we let it
+          // take a matrix.
+    const typename disable_if<is_matrix<image_type>,matrix_op<op_image_to_mat<image_type, typename image_traits<image_type>::pixel_type> > >::type mat (
+        const image_type& img 
     )
     {
-        typedef op_array2d_to_mat<array2d<T,MM> > op;
-        return matrix_op<op>(op(array));
+        typedef op_image_to_mat<image_type, typename image_traits<image_type>::pixel_type> op;
+        return matrix_op<op>(op(img));
+    }
+
+// ----------------------------------------------------------------------------------------
+
+    template <typename image_type>
+    struct op_image_view_to_mat : does_not_alias 
+    {
+        op_image_view_to_mat( const image_view<image_type>& img) : imgview(img){}
+
+        typedef typename image_traits<image_type>::pixel_type pixel_type;
+
+        const image_view<image_type>& imgview;
+
+        const static long cost = 1;
+        const static long NR = 0;
+        const static long NC = 0;
+        typedef pixel_type type;
+        typedef const pixel_type& const_ret_type;
+        typedef default_memory_manager mem_manager_type;
+        typedef row_major_layout layout_type;
+
+        const_ret_type apply (long r, long c ) const { return imgview[r][c]; }
+
+        long nr () const { return imgview.nr(); }
+        long nc () const { return imgview.nc(); }
+    }; 
+
+    template <
+        typename image_type
+        > 
+    const matrix_op<op_image_view_to_mat<image_type> > mat (
+        const image_view<image_type>& img 
+    )
+    {
+        typedef op_image_view_to_mat<image_type> op;
+        return matrix_op<op>(op(img));
+    }
+
+// ----------------------------------------------------------------------------------------
+
+    template <typename image_type>
+    struct op_const_image_view_to_mat : does_not_alias 
+    {
+        op_const_image_view_to_mat( const const_image_view<image_type>& img) : imgview(img){}
+
+        typedef typename image_traits<image_type>::pixel_type pixel_type;
+
+        const const_image_view<image_type>& imgview;
+
+        const static long cost = 1;
+        const static long NR = 0;
+        const static long NC = 0;
+        typedef pixel_type type;
+        typedef const pixel_type& const_ret_type;
+        typedef default_memory_manager mem_manager_type;
+        typedef row_major_layout layout_type;
+
+        const_ret_type apply (long r, long c ) const { return imgview[r][c]; }
+
+        long nr () const { return imgview.nr(); }
+        long nc () const { return imgview.nc(); }
+    }; 
+
+    template <
+        typename image_type
+        > 
+    const matrix_op<op_const_image_view_to_mat<image_type> > mat (
+        const const_image_view<image_type>& img 
+    )
+    {
+        typedef op_const_image_view_to_mat<image_type> op;
+        return matrix_op<op>(op(img));
     }
 
 // ----------------------------------------------------------------------------------------
@@ -418,6 +492,42 @@ namespace dlib
         return array;
     }
 
+// ----------------------------------------------------------------------------------------
+
+    template <typename T>
+    struct op_array2d_to_mat : does_not_alias 
+    {
+        op_array2d_to_mat( const T& array_) : array(array_){}
+
+        const T& array;
+
+        const static long cost = 1;
+        const static long NR = 0;
+        const static long NC = 0;
+        typedef typename T::type type;
+        typedef const typename T::type& const_ret_type;
+        typedef typename T::mem_manager_type mem_manager_type;
+        typedef row_major_layout layout_type;
+
+        const_ret_type apply (long r, long c ) const { return array[r][c]; }
+
+        long nr () const { return array.nr(); }
+        long nc () const { return array.nc(); }
+    }; 
+
+    // Note that we have this version of mat() because it's slightly faster executing
+    // than the general one that handles any generic image.  This is because it avoids
+    // calling image_data() which for array2d involves a single if statement but this
+    // version here has no if statement in its construction.
+    template < typename T, typename MM >
+    const matrix_op<op_array2d_to_mat<array2d<T,MM> > > mat (
+        const array2d<T,MM>& array
+    )
+    {
+        typedef op_array2d_to_mat<array2d<T,MM> > op;
+        return matrix_op<op>(op(array));
+    }
+
     template <
         typename array_type
         >

dlib/matrix/matrix_mat_abstract.h

@@ -28,14 +28,20 @@ namespace dlib
 // ----------------------------------------------------------------------------------------
 
     template <
-        typename T,
-        typename MM
+        typename image_type
         >
     const matrix_exp mat (
-        const array2d<T,MM>& array
+        const image_type& img
     );
     /*!
+        requires
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h or image_type is a image_view or
+              const_image_view object.
         ensures
+            - This function converts any kind of generic image object into a dlib::matrix
+              expression.  Therefore, it is capable of converting objects like dlib::array2d
+              of dlib::cv_image.
             - returns a matrix R such that:
                 - R.nr() == array.nr() 
                 - R.nc() == array.nc()

dlib/opencv/cv_image.h

@@ -7,6 +7,7 @@
 #include "../algs.h"
 #include "../pixel.h"
 #include "../matrix/matrix_mat.h"
+#include "../image_processing/generic_image.h"
 
 namespace dlib
 {
@@ -139,6 +140,51 @@ namespace dlib
 
 // ----------------------------------------------------------------------------------------
 
+// Define the global functions that make cv_image a proper "generic image" according to
+// ../image_processing/generic_image.h
+    template <typename T>
+    struct image_traits<cv_image<T> >
+    {
+        typedef T pixel_type;
+    };
+
+    template <typename T>
+    inline long num_rows( const cv_image<T>& img) { return img.nr(); }
+    template <typename T>
+    inline long num_columns( const cv_image<T>& img) { return img.nc(); }
+
+    template <typename T>
+    inline void* image_data(
+        cv_image<T>& img
+    )
+    {
+        if (img.size() != 0)
+            return &img[0][0];
+        else
+            return 0;
+    }
+
+    template <typename T>
+    inline const void* image_data(
+        const cv_image<T>& img
+    )
+    {
+        if (img.size() != 0)
+            return &img[0][0];
+        else
+            return 0;
+    }
+
+    template <typename T>
+    inline long width_step(
+        const cv_image<T>& img
+    ) 
+    { 
+        return img.width_step(); 
+    }
+
+// ----------------------------------------------------------------------------------------
+
 }
 
 #endif // DLIB_CvIMAGE_H_

dlib/opencv/to_open_cv.h

@@ -19,49 +19,20 @@ namespace dlib
         image_type& img
     )
     {
-        if (img.size() == 0)
+        if (image_size(img) == 0)
             return cv::Mat();
 
-        typedef typename image_type::type type;
+        typedef typename image_traits<image_type>::pixel_type type;
         if (pixel_traits<type>::num == 1)
         {
-            return cv::Mat(img.nr(), img.nc(), cv::DataType<type>::type, (void*)&img[0][0], img.width_step());
+            return cv::Mat(num_rows(img), num_columns(img), cv::DataType<type>::type, image_data(img), width_step(img));
         }
         else
         {
             int depth = sizeof(typename pixel_traits<type>::basic_pixel_type)*8;
             int channels = pixel_traits<type>::num;
             int thetype = CV_MAKETYPE(depth, channels);
-            return cv::Mat(img.nr(), img.nc(), thetype, (void*)&img[0][0], img.width_step());
-        }
-    }
-
-// ----------------------------------------------------------------------------------------
-
-    template <
-        typename T,
-        long NR,
-        long NC,
-        typename MM
-        >
-    cv::Mat toMat (
-        matrix<T,NR,NC,MM>& img
-    )
-    {
-        if (img.size() == 0)
-            return cv::Mat();
-
-        typedef T type;
-        if (pixel_traits<type>::num == 1)
-        {
-            return cv::Mat(img.nr(), img.nc(), cv::DataType<type>::type, (void*)&img(0,0), img.nc()*sizeof(type));
-        }
-        else
-        {
-            int depth = sizeof(typename pixel_traits<type>::basic_pixel_type)*8;
-            int channels = pixel_traits<type>::num;
-            int thetype = CV_MAKETYPE(depth, channels);
-            return cv::Mat(img.nr(), img.nc(), thetype, (void*)&img(0,0), img.nc()*sizeof(type));
+            return cv::Mat(num_rows(img), num_columns(img), thetype, image_data(img), width_step(img));
         }
     }
 

dlib/opencv/to_open_cv_abstract.h

@@ -15,9 +15,10 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == an implementation of dlib/array2d/array2d_kernel_abstract.h or
-              a dlib::matrix object which uses a row_major_layout.
-            - pixel_traits<typename image_type::type> is defined
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h or a dlib::matrix object which uses a
+              row_major_layout.
+            - pixel_traits is defined for the contents of img.
         ensures
             - returns an OpenCV Mat object which represents the same image as img.  This
               is done by setting up the Mat object to point to the same memory as img.