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

问题描述

我正在尝试用其他图层裁剪图层，但是，我不是创建蒙版 (B) 并裁剪图层 (A)，而是得到一个形状为 B 的裁剪图层 A，我想得到一个形状为 A 的图层以及通过 B 层裁剪创建的洞".

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

你必须创建一个遮罩来覆盖你想要保留的区域.这可以通过使用奇偶填充规则并为具有两个矩形的形状图层创建路径来完成.您可以像这样创建形状(两个矩形将是您的两个框架).然后你将它设置为掩码以获得你想要的结果.

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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