From 97e7217e06e8424304e668e4bfd2563d89c4a3d6 Mon Sep 17 00:00:00 2001
From: Sam Lantinga <slouken@libsdl.org>
Date: Tue, 3 Jan 2012 20:04:02 -0500
Subject: [PATCH] Fixed colorspace for ImageIO loading

albert

Test case: https://gist.github.com/1551241

It should output:

Code:
$ ./sdlimagetest
PixelFormat:  BitsPerPixel: 32,  BytesPerPixel: 4
  R/G/B/A mask: ff0000/ff00/ff/ff000000
  R/G/B/A loss: 0/0/0/0
  Colorkey: 0,  Alpha: 255
 FF0000FF
 FF0000FF
 FF0000FF
 FF0000FF
 FF0000FF
 FF0000FF
 FF0000FF
 FF0000FF
 FF0000FF
 FF0000FF


Output with bad SDL_image:

Code:

$ ./sdlimagetest
PixelFormat:
  BitsPerPixel: 32,  BytesPerPixel: 4
  R/G/B/A mask: ff0000/ff00/ff/ff000000
  R/G/B/A loss: 0/0/0/0
  Colorkey: 0,  Alpha: 255
 FF1514F4
 FF1514F4
 FF1514F4
 FF1514F4
 FF1514F4
 FF1514F4
 FF1514F4
 FF1514F4
 FF1514F4
 FF1514F4


And I searched a bit around and I found a fix in the Allegro code (http://codesearch.google.com/#w3aXj_apqFs/allegro/tags/5.0.0/addons/image/macosx.m&ct=rc&cd=3&q=CGColorSpaceCreateCalibratedRGB).

So I wrote a patch for SDL_image: https://gist.github.com/1551404
---
 IMG_ImageIO.m | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/IMG_ImageIO.m b/IMG_ImageIO.m
index ac615a67..d2f002c8 100644
--- a/IMG_ImageIO.m
+++ b/IMG_ImageIO.m
@@ -212,8 +212,25 @@ static CFDictionaryRef CreateHintDictionary(CFStringRef uti_string_hint)
     
     CGContextRef bitmap_context;
     CGBitmapInfo bitmap_info;
-    CGColorSpaceRef color_space = CGColorSpaceCreateDeviceRGB();
-    
+
+	/* This sets up a color space that results in identical values
+	 * as the image data itself, which is the same as the standalone
+	 * libpng loader.
+	 * Thanks to Allegro. :)
+	 */
+	CGFloat whitePoint[3] = { 1, 1, 1 };
+	CGFloat blackPoint[3] = { 0, 0, 0 };
+	CGFloat gamma[3] = { 2.2, 2.2, 2.2 };
+	CGFloat matrix[9] = {
+		1, 1, 1,
+		1, 1, 1,
+		1, 1, 1
+	};
+	CGColorSpaceRef color_space =
+		CGColorSpaceCreateCalibratedRGB(
+									whitePoint, blackPoint, gamma, matrix
+									);   
+	
     if (alpha == kCGImageAlphaNone ||
         alpha == kCGImageAlphaNoneSkipFirst ||
         alpha == kCGImageAlphaNoneSkipLast) {