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
{
CGRectrect = (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;
}
