How do I change a partially transparent image's color in iOS?

Question

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

Answer 1

I have updated the code above to account for retina resolution images:

- (UIImage *) changeColorForImage:(UIImage *)mask toColor:(UIColor*)color {

CGImageRef maskImage = mask.CGImage;
CGFloat width = mask.scale * mask.size.width;
CGFloat height = mask.scale * mask.size.height;
CGRect bounds = CGRectMake(0,0,width,height);

CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef bitmapContext = CGBitmapContextCreate(NULL, width, height, 8, 0, colorSpace, (CGBitmapInfo)kCGImageAlphaPremultipliedLast);
CGContextClipToMask(bitmapContext, bounds, maskImage);
CGContextSetFillColorWithColor(bitmapContext, color.CGColor);    
CGContextFillRect(bitmapContext, bounds);

CGImageRef mainViewContentBitmapContext = CGBitmapContextCreateImage(bitmapContext);
CGContextRelease(bitmapContext);

return [UIImage imageWithCGImage:mainViewContentBitmapContext scale:mask.scale orientation:UIImageOrientationUp];
}

Answer 2

The code in the question is working code. The bug was elsewhere.