在网格上旋转 CGPoint 的最佳方法是什么? [英] What is the best way to rotate a CGPoint on a grid?

问题描述

我想根据角度旋转屏幕上的 CGPoint，并且旋转锚定在另一个点上.想知道最有效的方法是什么?

I want to rotate a CGPoint on the screen depending on the angle and the rotation is anchored on another point. Was wondering what is the most efficient way of doing this?

推荐答案

你也可以这样用:

rotatedPoint = CGPointApplyAffineTransform(initialPoint, CGAffineTransformMakeRotation(angle));

要围绕自定义点执行旋转，您必须像 Adam 在他的回答中描述的那样.使用 CGAffineTransform 它必须看起来像:

to perform rotation around custom point you must do like Adam described in his answer. Using CGAffineTransform it must look something like:

CGAffineTransform translateTransform = CGAffineTransformMakeTranslation(customCenter.x, customCenter.y);
CGAffineTransform rotationTransform = CGAffineTransformMakeRotation(angle);

CGAffineTransform customRotation = CGAffineTransformConcat(CGAffineTransformConcat( CGAffineTransformInvert(translateTransform), rotationTransform), translateTransform);

rotatedPoint = CGPointApplyAffineTransform(initialPoint, customRotation);

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