Drawing a transparent circle on top of a UIImage - iPhone SDK

Question

I am having a lot of trouble trying to find out how to draw a transparent circle on top of a UIImage within my UIImageView. Google-ing gives me clues, but I still can\'t find a

Answer 1

One way would be to add a CAShapeLayer with a circular path, either directly to the layer of the UIImageView or as the layer of a new UIView that is added to the UIImageView.

If you actually want to modify the image, then create a mutable copy of it by drawing it into a CGBitmapContext then creating a new image from the modified bitmap.

CGPathRef circlePath = CGPathCreateMutable();
CGPathAddEllipseInRect( circlePath , NULL , CGRectMake( 0,0,20,20 ) );
CAShapeLayer *circle = [[CAShapeLayer alloc] init];
circle.path = circlePath;
circle.opacity = 0.5;
[myImageView.layer addSublayer:circle];
CGPathRelease( circlePath );
[circle release];