Image mask

gistfile1.m

- (UIImage *)imageWithMask:(UIImage *)maskImage andIsWhite:(BOOL)isWhite
{
  CGRect imageRect = CGRectMake(0, 0, maskImage.size.width, maskImage.size.height);
  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
  CGContextRef ctx = CGBitmapContextCreate(NULL, maskImage.size.width, maskImage.size.height, 8, 0, colorSpace, kCGImageAlphaPremultipliedLast);
  
  CGContextClipToMask(ctx, imageRect, maskImage.CGImage);
  if (isWhite) {
    CGContextSetRGBFillColor(ctx, 1, 1, 1, 1);
  } else {
    CGContextSetRGBFillColor(ctx, 0, 0, 0, 1);
  }
  
  CGContextFillRect(ctx, imageRect);

  CGImageRef imageRef = CGBitmapContextCreateImage(ctx);
  UIImage *image = [UIImage imageWithCGImage:imageRef];
  
  CGImageRelease(imageRef);
  CGContextRelease(ctx);
  CGColorSpaceRelease(colorSpace);
  
  return image;
}