CGPoint currentPoint = [touch locationInView:imageView];
UIGraphicsBeginImageContext(self.imageView.frame.size);
[imageView.image drawInRect:imageView.bounds]; 4
CGContextRef context = UIGraphicsGetCurrentContext();
CGRect cirleRect = CGRectMake(currentPoint.x-30, currentPoint.y-30,60,60);
CGContextAddArc(context,currentPoint.x, currentPoint.y,30,0,2*M_PI,0);
CGContextClip(context);
CGContextClearRect(context,cirleRect);
imageView.image=UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
