iOS设置圆角图片

1.实现方式

简易方式：

self.img1.layer.cornerRadius=self.img1.bounds.size.width/2;
self.img1.layer.masksToBounds=YES;

CoreGraphics剪裁方式

    UIGraphicsBeginImageContextWithOptions(image.size, NO, 0);
    UIBezierPath *path=[UIBezierPath bezierPathWithOvalInRect:CGRectMake(0, 0, image.size.width, image.size.height)];
    [path addClip];
    [image drawAtPoint:CGPointZero];
    UIImage * newImg = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    self.img1.image = newImg;

2.性能测试

利用Instruments->Core Animation
测试环境是iphone7plus ios11.4
显示列表，多个圆角图片

WechatIMG1.jpeg

A.使用简易模式

    self.img1.layer.cornerRadius=self.img1.bounds.size.width/2;
    self.img1.layer.masksToBounds=YES;
    self.img2.layer.cornerRadius=self.img2.bounds.size.width/2;
    self.img2.layer.masksToBounds=YES;
    self.img3.layer.cornerRadius=self.img3.bounds.size.width/2;
    self.img3.layer.masksToBounds=YES;
    self.img4.layer.cornerRadius=self.img4.bounds.size.width/2;
    self.img4.layer.masksToBounds=YES;
    self.img5.layer.cornerRadius=self.img5.bounds.size.width/2;
    self.img5.layer.masksToBounds=YES;
    self.img1.image = image;
    self.img2.image = image;
    self.img3.image = image;
    self.img4.image = image;
    self.img5.image = image;

快速滑动列表的时候，基本不掉帧，GPU使用率15左右。

1.png

B.裁剪方式

    UIGraphicsBeginImageContextWithOptions(image.size, NO, 0);
    UIBezierPath *path=[UIBezierPath bezierPathWithOvalInRect:CGRectMake(0, 0, image.size.width, image.size.height)];
    [path addClip];
    [image drawAtPoint:CGPointZero];
    UIImage * newImg = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    self.img1.image = newImg;
    self.img2.image = newImg;
    self.img3.image = newImg;
    self.img4.image = newImg;
    self.img5.image = newImg;

快速滑动列表的时候，卡顿明显，GPU使用率30左右。

2.png

是不是很诡异，和我们想的不太一样。
其实，如果使用CoreGraphics，最好异步绘制。

        dispatch_async(dispatch_get_global_queue(0, 0), ^{
        UIGraphicsBeginImageContextWithOptions(image.size, NO, 0);
        UIBezierPath *path=[UIBezierPath bezierPathWithOvalInRect:CGRectMake(0, 0, image.size.width, image.size.height)];
        [path addClip];
        [image drawAtPoint:CGPointZero];
        UIImage * newImg = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        dispatch_async(dispatch_get_main_queue(), ^{
            self.img1.image = newImg;
            self.img2.image = newImg;
            self.img3.image = newImg;
            self.img4.image = newImg;
            self.img5.image = newImg;
        });
    });

快速滑动列表的时候，虽然基本不掉帧，但是GPU使用率20左右。

3.png

综上所述：在当前测试环境下，简易方式设置圆角完全没有性能问题(系统对于该方法进行了优化)。