裁剪CAShapeLayer检索外部路径 [英] Crop a CAShapeLayer retrieving the external path

问题描述

我正在尝试与其他图层一起裁剪一个图层，但是，我不想创建一个蒙版(B)并裁剪该图层(A)以得到具有B形状的裁剪后的图层A，而是要获得一个具有A形状的图层以及通过裁剪B层而创建的洞".

I am trying to crop a layer with other, but, instead of creating a mask (B) and crop the layer (A) getting a cropped layer A with the shape of B, I want to get a layer with shape A and a 'hole' created by cropping with layer B.

*************               ***Layer A***
*  Layer A  *               *************
*   *****   *               ****    *****
*   * B *   *      ->       ****    ***** Layer A without shape B
*   *****   *               ****    *****
*           *               *************
*************               *************

如何获得裁剪后的图层A?

How can I get the cropped layer A?

推荐答案

您必须创建一个遮罩，遮盖您要保持的区域.这可以通过使用奇偶填充规则并为包含两个矩形的形状图层创建路径来完成.您可以创建这样的形状(其中两个矩形就是您的两个框架).然后将其设置为蒙版，以得到想要的结果.

You have to create a mask that covers the area that you want to keep. This can be done by using an even-odd fill rule and create a path for a shape layer with both rectangles. You can create the shape like this (where the two rectangles would be your two frames). Then you set this as the mask to get the result that you are after.

CAShapeLayer *maskWithHole = [CAShapeLayer layer];

// Both frames are defined in the same coordinate system
CGRect biggerRect = CGRectMake(30, 50, 120, 200);
CGRect smallerRect = CGRectMake(80, 100, 50, 80);

UIBezierPath *maskPath = [UIBezierPath bezierPath];
[maskPath moveToPoint:CGPointMake(CGRectGetMinX(biggerRect), CGRectGetMinY(biggerRect))];
[maskPath addLineToPoint:CGPointMake(CGRectGetMinX(biggerRect), CGRectGetMaxY(biggerRect))];
[maskPath addLineToPoint:CGPointMake(CGRectGetMaxX(biggerRect), CGRectGetMaxY(biggerRect))];
[maskPath addLineToPoint:CGPointMake(CGRectGetMaxX(biggerRect), CGRectGetMinY(biggerRect))];
[maskPath addLineToPoint:CGPointMake(CGRectGetMinX(biggerRect), CGRectGetMinY(biggerRect))];

[maskPath moveToPoint:CGPointMake(CGRectGetMinX(smallerRect), CGRectGetMinY(smallerRect))];
[maskPath addLineToPoint:CGPointMake(CGRectGetMinX(smallerRect), CGRectGetMaxY(smallerRect))];
[maskPath addLineToPoint:CGPointMake(CGRectGetMaxX(smallerRect), CGRectGetMaxY(smallerRect))];
[maskPath addLineToPoint:CGPointMake(CGRectGetMaxX(smallerRect), CGRectGetMinY(smallerRect))];
[maskPath addLineToPoint:CGPointMake(CGRectGetMinX(smallerRect), CGRectGetMinY(smallerRect))];

[maskWithHole setPath:[maskPath CGPath]];
[maskWithHole setFillRule:kCAFillRuleEvenOdd];
[maskWithHole setFillColor:[[UIColor orangeColor] CGColor]];

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