如何设置裁剪矩形或区域 [英] How to set up a clipping rectangle or area

问题描述

如何在iOS drawRect中设置，修改和清除一个裁剪矩形，以便将线，文本，图像等的通用CG图纸裁剪到视图的一小部分？

How does one set up, modify, and clear a clipping rectangle inside a iOS drawRect for clipping generic CG drawing of lines, text, images, etc. to a small portion of a view?

是否可以使用由多个矩形和圆形组成的更复杂的裁剪区域？

Is it possible to use a more complex clipping region that is a composite of a bunch of rectangles and circles?

推荐答案

您可以使用任意路径设置剪切区域，而不仅限于矩形。以下是一些实现方法：

You can set a clipping area with arbitrary paths, not restricted to rectangles. The followings are some ways of doing it:

1. 您可以绘制任意路径并设置剪切区域。例如：

1. You can draw an arbitrary path and set a clipping area with it. For example:

CGContextBeginPath(context);
//draw a path here
CGContextClosePath(context);
CGContextClip(context);
//following drawing on the context will be clipped

如果要使用蒙版图像设置剪切区域，使用CGContextClipToMask方法。

If you want to use a mask image to set a clipping area, use CGContextClipToMask method.

有关更多信息，请参见Apple的 QuartzDemo示例项目用法。

See Apple's 'QuartzDemo' sample project for more usages.

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