围绕外部点的CGAffineTransformMakeRotation [英] CGAffineTransformMakeRotation around external point

问题描述

有没有办法使用CGAffineTranformMAkeRotation围绕外部点旋转UIImage？
tnx很多！

解决方案

这是一个使用与CoreGraphics CGAffineTransform API格式相同格式的函数。 / p>

这完全适用于其他RotateAt（）API应该如何工作。

该操作代表相当于以下规范：translate（pt.x，pt.y）;旋转（角度）; translate（-pt.x，-pt.y）;

  CGAffineTransform CGAffineTransformMakeRotationAt（CGFloat angle，CGPoint pt）{
 const CGFloat fx = pt.x，fy = pt.y，fcos = cos（角度），fsin = sin（角度）; 
返回CGAffineTransformMake（fcos，fsin，-fsin，fcos，fx  -  fx * fcos + fy * fsin，fy  -  fx * fsin  -  fy * fcos）; 
} 
  

就像 CGAffineTransformMakeRotation（），角度是弧度，而不是度数。

are there a way for rotate UIImage around external point using CGAffineTranformMAkeRotation? tnx a lot!

解决方案

Here is a function that uses the same format as the CoreGraphics CGAffineTransform API format.

This works exactly how other "RotateAt()" APIs should work.

The operation represents the equivalent of the following specification: translate(pt.x, pt.y); rotate(angle); translate(-pt.x, -pt.y);

CGAffineTransform CGAffineTransformMakeRotationAt(CGFloat angle, CGPoint pt){
    const CGFloat fx = pt.x, fy = pt.y, fcos = cos(angle), fsin = sin(angle);
    return CGAffineTransformMake(fcos, fsin, -fsin, fcos, fx - fx * fcos + fy * fsin, fy - fx * fsin - fy * fcos);
}

Just like with CGAffineTransformMakeRotation(), angle is in radians, not degrees.

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