iphone sdk CGAffineTransform 获取对象的旋转角度 [英] iphone sdk CGAffineTransform getting the angle of rotation of an object

问题描述

如何计算任何给定对象(即 uiimageview)的旋转角度?

how do i calculate the angle of rotation for any given object (ie a uiimageview)?

推荐答案

从技术上讲你不能，因为变换可以包括一个 skew 操作，将图像变成平行四边形，并且旋转角度是'不再定义.

Technically you can't, because the transform can include a skew operation which turns the image into a parallelogram and the rotation angle isn't defined anymore.

无论如何，由于旋转矩阵生成

Anyway, since the rotation matrix generates

 cos(x)  sin(x)   0
-sin(x)  cos(x)   0
   0        0     1

你可以用

return atan2(transform.b, transform.a);

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