CGPath 裁剪答案

【问题标题】：CGPath clippingCGPath 裁剪
【发布时间】：2016-04-18 08:08:48
【问题描述】：

我想做类似的东西：

我尝试了以下代码：

CGMutablePathRef path = CGPathCreateMutable();
CGPathAddLines(path, &CGAffineTransformIdentity, points, sizeof points / sizeof *points);

CGMutablePathRef strokePath = (CGMutablePathRef)CGPathCreateCopyByStrokingPath(path, &CGAffineTransformIdentity, data.lineWidth, kCGLineCapRound, kCGLineJoinMiter, 4.f);

for(NSInteger i = 0; i < [data.values count]; i++) {
    CGRect rect = CGRectMake(points[i].x - data.dotRadius, points[i].y - data.dotRadius, data.dotRadius * 2, data.dotRadius * 2);
    CGPathAddEllipseInRect(strokePath, &CGAffineTransformIdentity, rect);
    CGPathAddEllipseInRect(strokePath, &CGAffineTransformIdentity, CGRectInset(rect, data.lineWidth, data.lineWidth));
}

然后绘制这条路径：

CAShapeLayer *layer = self.layers[line];
layer.path = strokePath;
layer.strokeColor = nil;
layer.fillColor = data.lineColor.CGColor;
layer.fillRule = kCAFillRuleEvenOdd;

Bt 给出类似的东西：

有谁知道我如何实现这一目标？

【问题讨论】：

标签： ios objective-c core-graphics

【解决方案1】：

画线和圆，不是作为复合路径，而是作为两条线和一个圆（并且没有任何填充规则）。然后通过使用kCGBlendModeClear 绘制一个较小的实心圆来“打出”圆中心的孔。

或者，首先剪掉圆心的孔。然后画线和圆。

【讨论】：

看我的书，从这里开始：apeth.com/iOSBook/ch15.html#_paths_and_drawing 箭头轴末端三角形缺口的两种切法，本节和下节，正是你想要的做。
谢谢，这确实可行。我最终做的有点不同，见下文。

【解决方案2】：

最后使用图层蒙版：

CGMutablePathRef path = CGPathCreateMutable();
CGPathAddLines(path, &CGAffineTransformIdentity, points, sizeof points / sizeof *points);

CGMutablePathRef dotPath = CGPathCreateMutable();
for(NSInteger i = 0; i < [data.values count]; i++) {
    CGRect rect = CGRectMake(points[i].x - data.dotRadius, points[i].y - data.dotRadius, data.dotRadius * 2, data.dotRadius * 2);
    CGPathAddEllipseInRect(dotPath, &CGAffineTransformIdentity, rect);
    CGPathAddEllipseInRect(dotPath, &CGAffineTransformIdentity, CGRectInset(rect, data.lineWidth, data.lineWidth));
}
CGPathAddPath(path, &CGAffineTransformIdentity, dotPath);

CGMutablePathRef maskPath = CGPathCreateMutable();
CGPathAddRect(maskPath, &CGAffineTransformIdentity, CGRectMake(0, 0, self.frame.size.width, self.frame.size.height));
CGPathAddPath(maskPath, &CGAffineTransformIdentity, dotPath);


CAShapeLayer *layer = self.layers[line];
layer.path = strokePath;
layer.lineWidth = 2;
layer.strokeColor = data.lineColor.CGColor;
layer.fillColor = nil;
layer.fillRule = kCAFillRuleEvenOdd;

CAShapeLayer *maskLayer = [CAShapeLayer layer];
maskLayer.path = maskPath;
maskLayer.fillRule = kCAFillRuleEvenOdd;
layer.mask = maskLayer;

【讨论】：