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

This has got to be the simplest solution:

CGFloat r = 150;

UILabel *lbl = [[UILabel alloc] initWithFrame:CGRectMake(0,0,1.5*r,1.5*r)];
lbl.text = @"●";
lbl.transform = CGAffineTransformMakeTranslation(0.0f, -r/6);
lbl.textAlignment = UITextAlignmentCenter;
lbl.backgroundColor = [UIColor clearColor];
lbl.textColor = [UIColor redColor];
lbl.font = [UIFont systemFontOfSize:2*r];
lbl.alpha = 0.5;
lbl.center = self.view.center;
[self.view addSubview:lbl];