Changed code around so that the save_png.h header file doesn't need to #include png.h.

I did this because png.h will cause the compile to fail if the user #includes setjmp.h
along with png.h.

dlib/all/source.cpp

@@ -47,6 +47,7 @@
 
 #ifdef DLIB_PNG_SUPPORT
 #include "../image_loader/png_loader.cpp"
+#include "../image_saver/save_png.cpp"
 #endif
 
 #ifdef DLIB_JPEG_SUPPORT

dlib/image_saver/save_png.cpp

+// Copyright (C) 2011  Davis E. King (davis@dlib.net)
+// License: Boost Software License   See LICENSE.txt for the full license.
+#ifndef DLIB_SAVE_PnG_CPP__
+#define DLIB_SAVE_PnG_CPP__
+
+// only do anything with this file if DLIB_PNG_SUPPORT is defined
+#ifdef DLIB_PNG_SUPPORT
+
+#include "save_png.h"
+#include <cstdio>
+#include <png.h>
+
+namespace dlib
+{
+    // Don't do anything when libpng calls us to tell us about an error.  Just return to 
+    // our own code and throw an exception (at the long jump target).
+    void png_reader_user_error_fn_silent(png_structp  png_struct, png_const_charp ) 
+    {
+        longjmp(png_jmpbuf(png_struct),1);
+    }
+    void png_reader_user_warning_fn_silent(png_structp , png_const_charp ) 
+    {
+    }
+
+    namespace impl
+    {
+        void impl_save_png (
+            const std::string& file_name,
+            std::vector<unsigned char*>& row_pointers,
+            const long width,
+            const png_type type,
+            const int bit_depth
+        )
+        {
+
+            FILE *fp;
+            png_structp png_ptr;
+            png_infop info_ptr;
+
+            /* Open the file */
+            fp = fopen(file_name.c_str(), "wb");
+            if (fp == NULL)
+                throw image_save_error("Unable to open " + file_name + " for writing.");
+
+            /* Create and initialize the png_struct with the desired error handler
+            * functions.  If you want to use the default stderr and longjump method,
+            * you can supply NULL for the last three parameters.  We also check that
+            * the library version is compatible with the one used at compile time,
+            * in case we are using dynamically linked libraries.  REQUIRED.
+            */
+            png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, &png_reader_user_error_fn_silent, &png_reader_user_warning_fn_silent);
+
+            if (png_ptr == NULL)
+            {
+                fclose(fp);
+                throw image_save_error("Error while writing PNG file " + file_name);
+            }
+
+            /* Allocate/initialize the image information data.  REQUIRED */
+            info_ptr = png_create_info_struct(png_ptr);
+            if (info_ptr == NULL)
+            {
+                fclose(fp);
+                png_destroy_write_struct(&png_ptr,  NULL);
+                throw image_save_error("Error while writing PNG file " + file_name);
+            }
+
+            /* Set error handling.  REQUIRED if you aren't supplying your own
+            * error handling functions in the png_create_write_struct() call.
+            */
+            if (setjmp(png_jmpbuf(png_ptr)))
+            {
+                /* If we get here, we had a problem writing the file */
+                fclose(fp);
+                png_destroy_write_struct(&png_ptr, &info_ptr);
+                throw image_save_error("Error while writing PNG file " + file_name);
+            }
+
+            int color_type = 0;
+            switch(type)
+            {
+                case png_type_rgb:       color_type = PNG_COLOR_TYPE_RGB; break;
+                case png_type_rgb_alpha: color_type = PNG_COLOR_TYPE_RGB_ALPHA; break;
+                case png_type_gray:      color_type = PNG_COLOR_TYPE_GRAY; break;
+                default:
+                    {
+                        fclose(fp);
+                        png_destroy_write_struct(&png_ptr, &info_ptr);
+                        throw image_save_error("Invalid color type");
+                    }
+            }
+
+
+            /* Set up the output control if you are using standard C streams */
+            png_init_io(png_ptr, fp);
+
+
+            const int png_transforms = PNG_TRANSFORM_IDENTITY;
+            const long height = row_pointers.size();
+
+
+            png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, color_type, PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);
+            png_set_rows(png_ptr, info_ptr, &row_pointers[0]);
+            png_write_png(png_ptr, info_ptr, png_transforms, NULL);
+
+            /* Clean up after the write, and free any memory allocated */
+            png_destroy_write_struct(&png_ptr, &info_ptr);
+
+            /* Close the file */
+            fclose(fp);
+        }
+    }
+}
+
+#endif // DLIB_PNG_SUPPORT
+
+#endif // DLIB_SAVE_PnG_CPP__
+
+