Question

我有一个UIBezierPath，我希望得到它的镜像。我怎么能做到这一点？

 // Method for generating a path
 UIBezierPath *myPath = [self generateAPathInBounds:boundingRect];

 // ? now I would like to mirror myPath ?

Answer 1

// Method for generating a path
UIBezierPath *myPath = [self generateAPathInBounds:boundingRect];

// Create two transforms, one to mirror across the x axis, and one to
// to translate the resulting path back into the desired boundingRect
CGAffineTransform mirrorOverXOrigin = CGAffineTransformMakeScale(-1.0f, 1.0f);
CGAffineTransform translate = CGAffineTransformMakeTranslation(boundingRect.width, 0);

// Apply these transforms to the path
[myPath applyTransform:mirrorOverXOrigin];
[myPath applyTransform:translate];

Answer 2

应该注意的是，您可能需要额外的代码，具体取决于您尝试镜像的路径在整个视图中的位置。

如果您正在尝试镜像占据整个视图的路径（或者至少与您正在镜像的轴的0坐标齐平），那么@ wbarksdale的答案将适合您。但是，如果您尝试镜像视图中间某处的整个视图的一小部分路径，那么您需要做更多工作。一般来说，算法就像这样

  //this rect should be the bounds of your path within its superviews
  //coordinate system
  let rect = myPath.bounds
  //first, you need to move the view all the way to the left
  //because otherwise, if you mirror it in its current position, 
  //the view will be thrown way off screen to the left
  path.apply(CGAffineTransform(translationX: -rect.origin.x, y: 0))
  //then you mirror it
  path.apply(CGAffineTransform(scaleX: -1, y: 1))
  //then, after its mirrored, move it back to its original position
  path.apply(CGAffineTransform(translationX: rect.origin.x + rect.width, y: 0))

一般来说，算法应该是

将路径移动到视图的最左侧或最顶部取决于您是使用CGAffineTransform(translateX....)
使用CGAffineTransform(scaleX....
使用CGAffineTransform(translateX....)

Answer 3

我认为您的path不以(0,0)为中心，此代码是正确的：

// Method for generating a path
UIBezierPath *myPath = [self generateAPathInBounds:boundingRect];

// Create two transforms, one to mirror across the x axis, and one to
// to translate the resulting path back into the desired boundingRect
CGAffineTransform mirrorOverXOrigin = CGAffineTransformMakeScale(-1.0f, 1.0f);
CGAffineTransform translate = CGAffineTransformMakeTranslation(CGRectGetMidX(boundingRect), 0);
CGAffineTransform translateBack = CGAffineTransformMakeTranslation(-CGRectGetMidX(boundingRect), 0);

// Apply these transforms to the path
[myPath applyTransform:translate];
[myPath applyTransform:mirrorOverXOrigin];
[myPath applyTransform:translateBack];

如何镜像UIBezierPath？

3 个答案: