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; }
