iOS 常用的圆角处理方式总结

最简单的方法，是让UI提供带圆角的图片
以下几种是通过代码设置的，均可以避免触发离屏渲染，提高性能

• 通过在ImageView的layer设置圆角

        let btn0 = UIButton(type: .custom)
        btn0.frame = CGRect(x: 100, y: 60, width: 100, height: 100)
        //设置圆角
        btn0.layer.cornerRadius = 50
        self.view.addSubview(btn0)
        //设置背景图片
        btn0.setImage(UIImage(named: "mouse"), for: .normal)
        //裁剪
        btn0.layer.masksToBounds = true

改为

        let btn0 = UIButton(type: .custom)
        btn0.frame = CGRect(x: 100, y: 60, width: 100, height: 100)
        //设置圆角
        btn0.imageView?.layer.cornerRadius = 50
        self.view.addSubview(btn0)
        //设置背景图片
        btn0.setImage(UIImage(named: "mouse"), for: .normal)
        //裁剪
        btn0.imageView?.layer.masksToBounds = true

• 通过贝塞尔曲线画圆角

extension UIImage{
//    贝塞尔曲线
    func roundedCornerImageWithCornerRadius(_ cornerRadius: inout CGFloat) -> UIImage{
        let  w = self.size.width
        let  h = self.size.height
        let scale = UIScreen.main.scale
        
        //防止圆角半径小于0，或者大于宽/高中较小的值
        if cornerRadius < 0 {
            cornerRadius = 0
        }else if cornerRadius >  min(w, h){
            cornerRadius = min(w, h) / 2
        }
        
        var image: UIImage?
        let imageFrame = CGRect(x: 0, y: 0, width: w, height: h)
        UIGraphicsBeginImageContextWithOptions(self.size, false, scale)
        UIBezierPath.init(roundedRect: imageFrame, cornerRadius: cornerRadius).addClip()
        
        self.draw(in: imageFrame)
        image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        
        return image!
    }
}

• 添加mask设置圆角

func addMaskToBounds(_ maskBounds: CGRect, _ cornerRadius: inout CGFloat) -> UIImage{
        let w = maskBounds.size.width
        let h = maskBounds.size.height
        let size = maskBounds.size
        let scale = UIScreen.main.scale
        let imageRect = CGRect(x: 0, y: 8, width: w, height: h)
        
        
        if cornerRadius < 0{
            cornerRadius = 0
        }else if cornerRadius >  min(w, h){
            cornerRadius = min(w, h) / 2
        }
        
        let image = UIImage.init(named: "mouse")
        
        UIGraphicsBeginImageContextWithOptions(size, false, scale)
        UIBezierPath.init(roundedRect: imageRect, cornerRadius: cornerRadius).addClip()
        
        image?.draw(in: imageRect)
        let roundImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        
        return roundImage!
        
    }

• 利用YYWebImage处理圆角

UIImage(named: "mouse")?.yy_image(byRoundCornerRadius: cornerRadius3)

以下是YYWebImage 中圆角处理的详细逻辑

- (UIImage *)yy_imageByRoundCornerRadius:(CGFloat)radius
                                 corners:(UIRectCorner)corners
                             borderWidth:(CGFloat)borderWidth
                             borderColor:(UIColor *)borderColor
                          borderLineJoin:(CGLineJoin)borderLineJoin {
    
    if (corners != UIRectCornerAllCorners) {
        UIRectCorner tmp = 0;
        if (corners & UIRectCornerTopLeft) tmp |= UIRectCornerBottomLeft;
        if (corners & UIRectCornerTopRight) tmp |= UIRectCornerBottomRight;
        if (corners & UIRectCornerBottomLeft) tmp |= UIRectCornerTopLeft;
        if (corners & UIRectCornerBottomRight) tmp |= UIRectCornerTopRight;
        corners = tmp;
    }
    
    UIGraphicsBeginImageContextWithOptions(self.size, NO, self.scale);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);
    CGContextScaleCTM(context, 1, -1);
    CGContextTranslateCTM(context, 0, -rect.size.height);
    
    CGFloat minSize = MIN(self.size.width, self.size.height);
    if (borderWidth < minSize / 2) {
        UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:CGRectInset(rect, borderWidth, borderWidth) byRoundingCorners:corners cornerRadii:CGSizeMake(radius, borderWidth)];
        [path closePath];
        
        CGContextSaveGState(context);
        [path addClip];
        CGContextDrawImage(context, rect, self.CGImage);
        CGContextRestoreGState(context);
    }
    
    if (borderColor && borderWidth < minSize / 2 && borderWidth > 0) {
        CGFloat strokeInset = (floor(borderWidth * self.scale) + 0.5) / self.scale;
        CGRect strokeRect = CGRectInset(rect, strokeInset, strokeInset);
        CGFloat strokeRadius = radius > self.scale / 2 ? radius - self.scale / 2 : 0;
        UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:strokeRect byRoundingCorners:corners cornerRadii:CGSizeMake(strokeRadius, borderWidth)];
        [path closePath];
        
        path.lineWidth = borderWidth;
        path.lineJoinStyle = borderLineJoin;
        [borderColor setStroke];
        [path stroke];
    }
    
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}