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?
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问题描述
我想根据角度在屏幕上旋转CGPoint,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
您也可以使用:
rotatedPoint = CGPointApplyAffineTransform(initialPoint, CGAffineTransformMakeRotation(angle));
编辑:要围绕自定义点执行旋转,你必须像他在答案中描述的那样做。使用CGAffineTransform它必须类似于:
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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