在drawRect中使用iOS反转掩码 [英] iOS invert mask in drawRect

问题描述

使用下面的代码，我成功地屏蔽了我绘图的一部分，但它与我想要屏蔽的相反。这掩盖了绘图的内部，我想掩盖外部。有没有一种简单的方法来反转这个掩码？

With the code below, I am successfully masking part of my drawing, but it's the inverse of what I want masked. This masks the inner portion of the drawing, where I would like to mask the outer portion. Is there a simple way to invert this mask?

myPath 下面是 UIBezierPath 。

CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];
CGMutablePathRef maskPath = CGPathCreateMutable();
CGPathAddPath(maskPath, nil, myPath.CGPath);
[maskLayer setPath:maskPath];
CGPathRelease(maskPath);
self.layer.mask = maskLayer;

推荐答案

在形状图层上填充奇数（ maskLayer.fillRule = kCAFillRuleEvenOdd; ）你可以添加一个覆盖整个框架的大矩形，然后添加你正在掩盖的形状。这实际上会反转掩码。

With even odd filling on the shape layer (maskLayer.fillRule = kCAFillRuleEvenOdd;) you can add a big rectangle that covers the entire frame and then add the shape you are masking out. This will in effect invert the mask.

CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];
CGMutablePathRef maskPath = CGPathCreateMutable();
CGPathAddRect(maskPath, NULL, someBigRectangle); // this line is new
CGPathAddPath(maskPath, nil, myPath.CGPath);
[maskLayer setPath:maskPath];
maskLayer.fillRule = kCAFillRuleEvenOdd;         // this line is new
CGPathRelease(maskPath);
self.layer.mask = maskLayer;

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