Question

Is there a way I can check if a UIImage contains a single color? I have an application that renders text to an image, and if the image that is returned is completely white, I do not want to redraw the screen.

Is there a way to achieve this?

Regards,
EZFrag

Answer 1

Something like this might do the trick

- (BOOL)imageIsWhite:(UIImage *)img {
  CGImageRef imageRef = img.CGImage;
  NSData *data = (NSData *) CGDataProviderCopyData(CGImageGetDataProvider(imageRef));
  unsigned char *pixels = (unsigned char *)[data bytes];
  BOOL isWhite = YES;

  for(int i = 0; i < [data length]; i += 4) {
    if (!(pixels[i] == pixels[i+1] == pixels[i+2] == 255)) {
      isWhite = NO;
      break;
    }
  }
  return isWhite;
}