gistfile1.m

+ (UIImage *)iconImageFrom:(VKColoredAssetConfigObject *)iconObject
{
    UIImage *maskImage = iconObject.maskImage;
    UIImage *overlayImage = iconObject.overlayImage;
    
    CGSize size = maskImage.size;   
    CGFloat scale = [[UIScreen mainScreen] scale];
    CGRect rect = CGRectMake(0.0, 0.0, size.width * scale, size.height * scale);
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    
    // Create Context
    CGContextRef context = CGBitmapContextCreate(NULL, rect.size.width, rect.size.height, 8, 0, colorSpace, kCGImageAlphaPremultipliedLast);
    
    if (!context)
    {
        CGColorSpaceRelease(colorSpace);
        return nil;
    }
    
    // Draw
    {        
        CGContextAddRect(context, rect);
        CGContextClip(context);
        CGContextSaveGState(context);
        
        // Mask
        CGContextClipToMask(context, rect, maskImage.CGImage);

        // Gradient
        CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);
        CGContextRestoreGState(context);
        
        // Overlay
        CGContextDrawImage(context, rect, overlayImage.CGImage);
    }
    
    // Create resulting image
    CGImageRef resultImageRef = CGBitmapContextCreateImage(context);
    UIImage *resultImage = [[UIImage alloc] initWithCGImage:resultImageRef scale:scale orientation:UIImageOrientationUp];
    
    // Clean up
    CGImageRelease(resultImageRef);
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);
    
  return resultImage;
}