+
+#ifdef PNG_MNG_FEATURES_SUPPORTED
+/* Undoes intrapixel differencing */
+void /* PRIVATE */
+png_do_write_intrapixel(png_row_infop row_info, png_bytep row)
+{
+ png_debug(1, "in png_do_write_intrapixel");
+
+ if (
+ (row_info->color_type & PNG_COLOR_MASK_COLOR))
+ {
+ int bytes_per_pixel;
+ png_uint_32 row_width = row_info->width;
+ if (row_info->bit_depth == 8)
+ {
+ png_bytep rp;
+ png_uint_32 i;
+
+ if (row_info->color_type == PNG_COLOR_TYPE_RGB)
+ bytes_per_pixel = 3;
+ else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+ bytes_per_pixel = 4;
+ else
+ return;
+
+ for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
+ {
+ *(rp) = (png_byte)((*rp - *(rp+1))&0xff);
+ *(rp+2) = (png_byte)((*(rp+2) - *(rp+1))&0xff);
+ }
+ }
+ else if (row_info->bit_depth == 16)
+ {
+ png_bytep rp;
+ png_uint_32 i;
+
+ if (row_info->color_type == PNG_COLOR_TYPE_RGB)
+ bytes_per_pixel = 6;
+ else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+ bytes_per_pixel = 8;
+ else
+ return;
+
+ for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
+ {
+ png_uint_32 s0 = (*(rp ) << 8) | *(rp+1);
+ png_uint_32 s1 = (*(rp+2) << 8) | *(rp+3);
+ png_uint_32 s2 = (*(rp+4) << 8) | *(rp+5);
+ png_uint_32 red = (png_uint_32)((s0 - s1) & 0xffffL);
+ png_uint_32 blue = (png_uint_32)((s2 - s1) & 0xffffL);
+ *(rp ) = (png_byte)((red >> 8) & 0xff);
+ *(rp+1) = (png_byte)(red & 0xff);
+ *(rp+4) = (png_byte)((blue >> 8) & 0xff);
+ *(rp+5) = (png_byte)(blue & 0xff);
+ }
+ }
+ }
+}
+#endif /* PNG_MNG_FEATURES_SUPPORTED */
+#endif /* PNG_WRITE_SUPPORTED */