Added some functions for running a 3x3 separable filter on part of an image.

dlib/image_transforms/spatial_filtering.h

@@ -104,10 +104,110 @@ namespace dlib
 
 // ----------------------------------------------------------------------------------------
 
-}
+    template <
+        long size,
+        typename T,
+        typename in_image_type
+        >
+    inline void separable_3x3_filter_block_grayscale (
+        T (&block)[size][size],
+        const in_image_type& img,
+        const long& r,
+        const long& c,
+        const T& fe1, // separable filter end
+        const T& fm,  // separable filter middle 
+        const T& fe2 // separable filter end 2
+    ) 
+    {
+        // 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+size-1,r+size-1),
+            "\t void separable_3x3_filter_block_grayscale()"
+            << "\n\t The sub-window doesn't fit inside the given image."
+            << "\n\t get_rect(img):       " << get_rect(img) 
+            << "\n\t (c,r):               " << point(c,r) 
+            << "\n\t (c+size-1,r+size-1): " << point(c+size-1,r+size-1) 
+            );
 
-#endif // DLIB_SPATIAL_FILTERINg_H_
 
+        T row_filt[size+2][size];
+        for (long rr = 0; rr < size+2; ++rr)
+        {
+            for (long cc = 0; cc < size; ++cc)
+            {
+                row_filt[rr][cc] = get_pixel_intensity(img[r+rr-1][c+cc-1])*fe1 + 
+                                   get_pixel_intensity(img[r+rr-1][c+cc])*fm + 
+                                   get_pixel_intensity(img[r+rr-1][c+cc+1])*fe2;
+            }
+        }
 
+        for (long rr = 0; rr < size; ++rr)
+        {
+            for (long cc = 0; cc < size; ++cc)
+            {
+                block[rr][cc] = (row_filt[rr][cc]*fe1 + 
+                                row_filt[rr+1][cc]*fm + 
+                                row_filt[rr+2][cc]*fe2)/256;
+            }
+        }
+
+    }
+
+// ----------------------------------------------------------------------------------------
+
+    template <
+        long size,
+        typename T,
+        typename U,
+        typename in_image_type
+        >
+    inline void separable_3x3_filter_block_rgb (
+        T (&block)[size][size],
+        const in_image_type& img,
+        const long& r,
+        const long& c,
+        const U& fe1, // separable filter end
+        const U& fm,  // separable filter middle 
+        const U& fe2  // separable filter end 2
+    ) 
+    {
+        // 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+size-1,r+size-1),
+            "\t void separable_3x3_filter_block_grayscale()"
+            << "\n\t The sub-window doesn't fit inside the given image."
+            << "\n\t get_rect(img):       " << get_rect(img) 
+            << "\n\t (c,r):               " << point(c,r) 
+            << "\n\t (c+size-1,r+size-1): " << point(c+size-1,r+size-1) 
+            );
+
+        T row_filt[size+2][size];
+        for (long rr = 0; rr < size+2; ++rr)
+        {
+            for (long cc = 0; cc < size; ++cc)
+            {
+                row_filt[rr][cc].red   = img[r+rr-1][c+cc-1].red*fe1   + img[r+rr-1][c+cc].red*fm   + img[r+rr-1][c+cc+1].red*fe2;
+                row_filt[rr][cc].green = img[r+rr-1][c+cc-1].green*fe1 + img[r+rr-1][c+cc].green*fm + img[r+rr-1][c+cc+1].green*fe2;
+                row_filt[rr][cc].blue  = img[r+rr-1][c+cc-1].blue*fe1  + img[r+rr-1][c+cc].blue*fm  + img[r+rr-1][c+cc+1].blue*fe2;
+            }
+        }
+
+        for (long rr = 0; rr < size; ++rr)
+        {
+            for (long cc = 0; cc < size; ++cc)
+            {
+                block[rr][cc].red   = row_filt[rr][cc].red*fe1   + row_filt[rr+1][cc].red*fm   + row_filt[rr+2][cc].red*fe2;
+                block[rr][cc].green = row_filt[rr][cc].green*fe1 + row_filt[rr+1][cc].green*fm + row_filt[rr+2][cc].green*fe2;
+                block[rr][cc].blue  = row_filt[rr][cc].blue*fe1  + row_filt[rr+1][cc].blue*fm  + row_filt[rr+2][cc].blue*fe2;
+            }
+        }
+
+    }
+
+// ----------------------------------------------------------------------------------------
+
+}
+
+#endif // DLIB_SPATIAL_FILTERINg_H_
 
 

dlib/image_transforms/spatial_filtering_abstract.h

@@ -8,6 +8,8 @@
 namespace dlib
 {
 
+// ----------------------------------------------------------------------------------------
+
     template <
         typename in_image_type,
         typename out_image_type,
@@ -51,6 +53,76 @@ namespace dlib
             - #out_img.nr() == in_img.nr()
     !*/
 
+// ----------------------------------------------------------------------------------------
+
+    template <
+        long size,
+        typename T,
+        typename in_image_type
+        >
+    inline void separable_3x3_filter_block_grayscale (
+        T (&block)[size][size],
+        const in_image_type& img,
+        const long& r,
+        const long& c,
+        const T& fe1, 
+        const T& fm,  
+        const T& fe2 
+    );
+    /*!
+        requires
+            - T should be a scalar type
+            - shrink_rect(get_rect(img),1).contains(c,r)
+            - shrink_rect(get_rect(img),1).contains(c+size-1,r+size-1)
+        ensures
+            - Filters the image in the sub-window of img defined by a rectangle 
+              with its upper left corner at (c,r) and lower right at (c+size-1,r+size-1).
+            - The output of the filter is stored in #block.  Note that img will be 
+              interpreted as a grayscale image.
+            - The filter used is defined by the separable filter [fe1 fm fe2].  So the
+              spatial filter is thus:
+                fe1*fe1  fe1*fm  fe2*fe1
+                fe1*fm   fm*fm   fe2*fm
+                fe1*fe2  fe2*fm  fe2*fe2
+    !*/
+
+// ----------------------------------------------------------------------------------------
+
+    template <
+        long size,
+        typename T,
+        typename U,
+        typename in_image_type
+        >
+    inline void separable_3x3_filter_block_rgb (
+        T (&block)[size][size],
+        const in_image_type& img,
+        const long& r,
+        const long& c,
+        const U& fe1, 
+        const U& fm, 
+        const U& fe2
+    );
+    /*!
+        requires
+            - pixel_traits<typename in_image_type::type>::rgb == true
+            - 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)
+            - shrink_rect(get_rect(img),1).contains(c+size-1,r+size-1)
+        ensures
+            - Filters the image in the sub-window of img defined by a rectangle 
+              with its upper left corner at (c,r) and lower right at (c+size-1,r+size-1).
+            - The output of the filter is stored in #block.  Note that the filter is applied
+              to each color component independently.
+            - The filter used is defined by the separable filter [fe1 fm fe2].  So the
+              spatial filter is thus:
+                fe1*fe1  fe1*fm  fe2*fe1
+                fe1*fm   fm*fm   fe2*fm
+                fe1*fe2  fe2*fm  fe2*fe2
+    !*/
+
+// ----------------------------------------------------------------------------------------
 
 }