iOS图片圆角

一：通过设置layer属性，主要是cornerRadius和masksToBounds属性，但是这种方式影响性能，不推荐使用。

二：使用贝塞尔曲线UIBezierPath和Core Graphics框架画出一个圆角

// swift
        let imgView = UIImageView()
        imgView.frame = CGRect(x: 50, y: 100, width: UIScreen.main.bounds.width - 100, height: 300)
        imgView.image = UIImage(named: "timg.jpeg")
        //开始对imageView进行画图
        UIGraphicsBeginImageContextWithOptions(imgView.bounds.size, false, 1.0)
        //使用贝塞尔曲线画出一个圆形图
        UIBezierPath(roundedRect: imgView.bounds, cornerRadius: 20).addClip()
        imgView.draw(imgView.bounds)
        
        imgView.image = UIGraphicsGetImageFromCurrentImageContext()
        // 结束画图
        UIGraphicsEndImageContext()
        view.addSubview(imgView)



// OC
    UIImageView * imgView = [[UIImageView alloc] init];
    imgView.frame = CGRectMake(50, 100, UIScreen.mainScreen.bounds.size.width - 100, 300);
    imgView.image = [UIImage imageNamed:@"timg.jpeg"];
    //开始对imageView进行画图
    UIGraphicsBeginImageContextWithOptions(imgView.bounds.size, NO, 1.0);
    //使用贝塞尔曲线画出一个圆形图
    [[UIBezierPath bezierPathWithRoundedRect:imgView.bounds cornerRadius:20] addClip];
    [imgView drawRect:imgView.bounds];
    
    imgView.image = UIGraphicsGetImageFromCurrentImageContext();
    //结束画图
    UIGraphicsEndImageContext();
    [self.view addSubview:imgView];

三：使用CAShapeLayer和UIBezierPath设置圆角

// swift
        let imgView1 = UIImageView()
        imgView1.frame = CGRect(x: 50, y: 420, width: UIScreen.main.bounds.width - 100, height: 300)
        imgView1.image = UIImage(named: "timg.jpeg")
        let maskPath = UIBezierPath(roundedRect: imgView1.bounds, byRoundingCorners: .allCorners, cornerRadii: CGSize(width: 20, height: 20))
        let maskLayer = CAShapeLayer()
        // 设置大小
        maskLayer.frame = imgView1.bounds
        // 设置图形样子
        maskLayer.path = maskPath.cgPath
        imgView1.layer.mask = maskLayer
        view.addSubview(imgView1)



// OC
    UIImageView * imgView1 = [[UIImageView alloc] init];
    imgView1.frame = CGRectMake(50, 420, UIScreen.mainScreen.bounds.size.width - 100, 300);
    imgView1.image = [UIImage imageNamed:@"timg.jpeg"];
    UIBezierPath * maskPath = [UIBezierPath bezierPathWithRoundedRect:imgView1.bounds byRoundingCorners:UIRectCornerAllCorners cornerRadii:CGSizeMake(20, 20)];
    CAShapeLayer * maskLayer = [[CAShapeLayer alloc] init];
    // 设置大小
    maskLayer.frame = imgView1.bounds;
    // 设置图形样子
    maskLayer.path = maskPath.CGPath;
    imgView1.layer.mask = maskLayer;
    [self.view addSubview:imgView1];