Create UIImage from shadowed view while retaining alpha?

Question

I have a somewhat unusual problem. In my app, I am shadowing a UIImageView using basic Quartz2d layer shadowing. Here\'s my code:

imageView.la         


        

Answer 1

Add shadow path to view like this

[view.layer setShadowPath:[[UIBezierPath bezierPathWithRect:view.bounds] CGPath]]; //add path
view.layer.shadowColor = [[UIColor blackColor] CGColor];
view.layer.shadowOffset = CGSizeMake(x, y);
view.layer.shadowRadius = rad;
view.layer.shadowOpacity = 0.2f;

Answer 2

Try setting your UIImageView's backgroundColor to [UIColor clearColor] - this may enable your current solution to work.

imageView.backgroundColor = [UIColor clearColor];
UIGraphicsBeginImageContext(CGSizeMake(320, 396)); 
[imageView.layer renderInContext:UIGraphicsGetCurrentContext()]; 
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

Source: Converting a CGLayer to a *transparent* UIImage and PNG file in CoreGraphics iphone

Answer 3

I've had this issue before too. My solution was not to do an image, but instead to set the shadow path to just the outline of the view you are animating.

[imageView setContentMode:UIViewContentModeScaleAspectFit];
imageView.layer.masksToBounds = NO;
imageView.layer.shadowOffset = CGSizeMake(5, 5);
imageView.layer.shadowRadius = 200;
imageView.layer.shadowOpacity = 0.5;
CGRect rect = [self rectFromImageView:imageView];
imageView.layer.shadowPath = [UIBezierPath bezierPathWithRect:rect].CGPath;

Which uses the following function which assumes the image is set to content mode aspect fit:

-(CGRect)rectFromImageView:(UIImageView *)iv {
    CGRect rect = (CGRect){{0,0},iv.frame.size};
    if (iv.image.size.width/iv.frame.size.width > iv.image.size.height/iv.frame.size.height) {
        //rect.origin.x == 0
        CGFloat sf = iv.frame.size.width/iv.image.size.width;
        rect.size.height = sf*iv.image.size.height;
        rect.origin.y = floor((iv.frame.size.height - rect.size.height)/2);
    } else {
        //rect.origin.y == 0;
        CGFloat sf = iv.frame.size.height/iv.image.size.height;
        rect.size.width = sf*iv.image.size.width;
        rect.origin.x = floor((iv.frame.size.width - rect.size.width)/2);       
    }
    return rect;
}

If your image is just set to fill then just using the imageView.bounds should be sufficient