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iosobjective-ccolorstransparentmask

IOS: color only the transparent pixels

If I have an image with some transparent pixels, is there any possibility to color the transparent pixels with white and make the rest of the image transparent in objective-c?

Thanks!

Solution

  • I found a solution: 

    - (UIImage*)convertToInverseWhiteMask: (UIImage *) image {
    UIGraphicsBeginImageContextWithOptions(image.size, NO, image.scale);
    CGRect imageRect = CGRectMake(0.0f, 0.0f, image.size.width, image.size.height);
    CGContextRef ctx = UIGraphicsGetCurrentContext();

    // Draw a white background (for white mask)
    CGContextSetRGBFillColor(ctx, 1.0f, 1.0f, 1.0f, 1.0f);
    CGContextFillRect(ctx, imageRect);

    // Apply the source image's alpha
    [image drawInRect:imageRect blendMode:kCGBlendModeDestinationOut alpha:1.0f];

    UIImage* mask = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return mask; 
   }