UIImageView添加圆角

• 最直接的方法就是使用如下属性设置：

  imgView.layer.cornerRadius = 10;
  // 这一行代码是很消耗性能的
  imgView.clipsToBounds = YES;

  **这是离屏渲染（off-screen-rendering），消耗性能的**

• 给UIImage添加生成圆角图片的扩展API：这是on-screen-rendering

  - (UIImage *)imageWithCornerRadius:(CGFloat)radius {
  CGRect rect = (CGRect){0.f, 0.f, self.size};
  
  UIGraphicsBeginImageContextWithOptions(self.size, NO, UIScreen.mainScreen.scale);
  CGContextAddPath(UIGraphicsGetCurrentContext(),
   [UIBezierPath bezierPathWithRoundedRect:rect cornerRadius:radius].CGPath);
  CGContextClip(UIGraphicsGetCurrentContext());
  
  [self drawInRect:rect];
  UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
  
  UIGraphicsEndImageContext();
  
  return image;
  }

UIImageView添加圆角

原文：http://www.cnblogs.com/jiqiaochun/p/5948967.html