I have a single-color image that has partial transparency. I have both normal and @2X versions of the image. I would like to be able to tint the image a different color, in code. The code below works fine for the normal image, but the @2X ends up with artifacts. The normal image might have a similar issue If so, I can't detect it on account of resolution.
+(UIImage *) newImageFromMaskImage:(UIImage *)mask inColor:(UIColor *) color {
CGImageRef maskImage = mask.CGImage;
CGFloat width = mask.size.width;
CGFloat height = mask.size.height;
CGRect bounds = CGRectMake(0,0,width,height);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef bitmapContext = CGBitmapContextCreate(NULL, width, height, 8, 0, colorSpace, kCGImageAlphaPremultipliedLast);
CGContextClipToMask(bitmapContext, bounds, maskImage);
CGContextSetFillColorWithColor(bitmapContext, color.CGColor);
CGContextFillRect(bitmapContext, bounds);
CGImageRef mainViewContentBitmapContext = CGBitmapContextCreateImage(bitmapContext);
CGContextRelease(bitmapContext);
UIImage *result = [UIImage imageWithCGImage:mainViewContentBitmapContext];
return result;
}
If it matters, the mask image is loaded using UIImage imageNamed:. Also, I confirmed that the @2X image is loading when run on the retina simulator.
Update: The above code works. The artifacts I was seeing were caused by additional transforms done by the consumer of the images. This question could be deleted since it's not really a question anymore or left for posterity.
The code in the question is working code. The bug was elsewhere.