一下方法写在自定义的ImageView中.
// 创建一个图片上下文
UIGraphicsBeginImageContext(self.size);
// 指定半径
CGFloat radius = 50;
UIBezierPath *path =[UIBezierPath bezierPathWithRect:self.bounds];
UIBezierPath *circlePath = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(self.centerX - radius, self.centerY - radius, 2.0*radius, 2.0*radius) cornerRadius:radius];
[path appendPath:circlePath];
[path setUsesEvenOddFillRule:YES];
[path addClip]; // 裁剪
// 绘制图片到图片上下文中
[self.image drawInRect:self.bounds];
self.image = UIGraphicsGetImageFromCurrentImageContext();
//关闭图片上下文
UIGraphicsEndImageContext();
