不好的解决方案：

使用下面的方式会强制Core Animation提前渲染屏幕的离屏绘制, 而离屏绘制就会给性能带来负面影响，会有卡顿的现象出现。

self.view.layer.cornerRadius =5.0f;

self.view.layer.masksToBounds =YES;

正确的解决方案：使用绘图技术

- (UIImage*)circleImage {

UIGraphicsBeginImageContextWithOptions(self.size,NO,0.0); // NO代表透明

CGContextRefctx =UIGraphicsGetCurrentContext(); // 获得上下文

CGRectrect =CGRectMake(0,0,self.size.width,self.size.height);CGContextAddEllipseInRect(ctx, rect);

CGContextClip(ctx);  // 添加一个圆 裁剪

// 将图片画上去

[selfdrawInRect:rect];UIImage*image =UIGraphicsGetImageFromCurrentImageContext();

// 关闭上下文

UIGraphicsEndImageContext();returnimage;}

还有一种方案：使用了贝塞尔曲线"切割"个这个图片, 给UIImageView 添加了的圆角，其实也是通过绘图技术来实现的。

UIImageView*imageView = [[UIImageViewalloc] initWithFrame:CGRectMake(0,0,100,100)];imageView.center =CGPointMake(200,300);

UIImage*anotherImage = [UIImageimageNamed:@"image"];

UIGraphicsBeginImageContextWithOptions(imageView.bounds.size,NO,1.0);[[UIBezierPathbezierPathWithRoundedRect:imageView.bounds cornerRadius:50] addClip];

[anotherImage drawInRect:imageView.bounds];

imageView.image =UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

[self.view addSubview:imageView];