+
+Image *
+readPNG(const char *filename)
+{
+ FILE *fp;
+ png_structp png_ptr;
+ png_infop info_ptr;
+ png_infop end_info;
+ Image *image;
+
+ fp = fopen(filename, "rb");
+ if (!fp)
+ goto no_fp;
+
+ png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
+ if (!png_ptr)
+ goto no_png;
+
+ info_ptr = png_create_info_struct(png_ptr);
+ if (!info_ptr) {
+ png_destroy_read_struct(&png_ptr, NULL, NULL);
+ goto no_png;
+ }
+
+ end_info = png_create_info_struct(png_ptr);
+ if (!end_info) {
+ png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
+ goto no_png;
+ }
+
+ if (setjmp(png_jmpbuf(png_ptr))) {
+ png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
+ goto no_png;
+ }
+
+ png_init_io(png_ptr, fp);
+
+ png_read_info(png_ptr, info_ptr);
+
+ png_uint_32 width, height;
+ int bit_depth, color_type, interlace_type, compression_type, filter_method;
+
+ png_get_IHDR(png_ptr, info_ptr,
+ &width, &height,
+ &bit_depth, &color_type, &interlace_type,
+ &compression_type, &filter_method);
+
+ image = new Image(width, height);
+ if (!image)
+ goto no_image;
+
+ /* Convert to RGBA8 */
+ if (color_type == PNG_COLOR_TYPE_PALETTE)
+ png_set_palette_to_rgb(png_ptr);
+ if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
+ png_set_expand_gray_1_2_4_to_8(png_ptr);
+ if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
+ png_set_tRNS_to_alpha(png_ptr);
+ if (bit_depth == 16)
+ png_set_strip_16(png_ptr);
+
+ for (unsigned y = 0; y < height; ++y) {
+ png_bytep row = (png_bytep)(image->pixels + y*width*4);
+ png_read_row(png_ptr, row, NULL);
+ }
+
+ png_read_end(png_ptr, info_ptr);
+ png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
+ fclose(fp);
+ return image;
+
+no_image:
+ png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
+no_png:
+ fclose(fp);
+no_fp:
+ return NULL;
+}
+
+