Scaling images for the web, maintaining colorspace when reasonable

gistfile1.m

- (CGImageRef)renderImage:(CIImage *)scaledImage fromSource:(CIImage *)sourceImage;
{
    // We want sRGB as fallback output colorspace
    CGColorSpaceRef colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceSRGB);
    
    CIContext *context = [CIContext contextWithCGContext:nil
                                                 options:[NSDictionary dictionaryWithObjectsAndKeys:
                                                          colorSpace, kCIContextOutputColorSpace,
                                                          nil]];
    
    CFRelease(colorSpace); colorSpace = NULL;

    // Only 10.6+ is willing to divulge image colorspace
    if ([image respondsToSelector:@selector(colorSpace)])
    {
        colorSpace = [image colorSpace];
    }
    
    CGImageRef result = NULL;
    if (colorSpace)
    {
        // Web browsers only support RGB and monochrome color spaces
        CGColorSpaceModel model = CGColorSpaceGetModel(colorSpace);
        if (model == kCGColorSpaceModelRGB || model == kCGColorSpaceModelMonochrome)
        {
            result = [[self sharedContext] createCGImage:scaledImage
                                                fromRect:[scaledImage extent]
                                                  format:kCIFormatARGB8
                                              colorSpace:colorSpace];
        }
    }
    
    if (!result)
    {
        result = [coreImageContext createCGImage:scaledImage fromRect:[scaledImage extent]];
    }
    
    return result;
}