iOS 切圆角

//初始化一个图片视图
UIImageView * view = [[UIImageView alloc] init];

CGRect rect = view.bounds;
CGSize size = rect.size;

UIGraphicsBeginImageContextWithOptions(size, NO, 0.0);

[[UIBezierPath bezierPathWithRoundedRect:rect cornerRadius:size.width] addClip];

[view drawRect:rect];

view.image = UIGraphicsGetImageFromCurrentImageContext();  

UIGraphicsEndImageContext();