self.imageView.opaque = YES;
self.scrollView.opaque = YES;

- (UIImage *)optimizedImageFromImage:(UIImage *)image
{
    CGSize imageSize = image.size;
    UIGraphicsBeginImageContextWithOptions( imageSize, opaque, scale );
    [image drawInRect: CGRectMake( 0, 0, imageSize.width, imageSize.height )];
    UIImage *optimizedImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return optimizedImage;
}

func optimizedImage(from image: UIImage) -> UIImage {
    let imageSize: CGSize = image.size
    UIGraphicsBeginImageContextWithOptions(imageSize, true, 1) // 1 is the scalling size @1x or @2x depending on need
    image.draw(in: CGRect(x: 0, y: 0, width: imageSize.width, height: imageSize.height))
    let optimizedImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return optimizedImage ?? UIImage()
}