ios 如何在 Swift 中应用多个转换

How to apply multiple transforms in Swift

提问by Suragch

I would like to apply multiple transforms to a UIView(or subclass of UIView), such as translate, rotate, and scale. I know that two transforms can be applied with CGAffineTransformConcat, but how do I do it if I have three or more transforms?

我想对一个UIView（或 的子类UIView）应用多个变换，例如平移、旋转和缩放。我知道可以应用两个转换CGAffineTransformConcat，但是如果我有三个或更多转换，我该怎么做？

I have seen these questions:

我见过这些问题：

• Applying multiple transforms to a UIView / CALayer
• Using Multiple CGAffineTransforms On Text Matrix

• 对 UIView / CALayer 应用多个变换
• 在文本矩阵上使用多个 CGAffineTransforms

but these questions are asking something different, and the given answers just talk about applying two transforms with CGAffineTransformConcat. Also, they use Objective-C rather than Swift.

但是这些问题提出了一些不同的问题，给出的答案只是谈论使用CGAffineTransformConcat. 此外，他们使用 Objective-C 而不是 Swift。

回答by Suragch

You can apply multiple transforms by stacking them on top of each other.

您可以通过将它们堆叠在一起来应用多个变换。

var t = CGAffineTransform.identity
t = t.translatedBy(x: 100, y: 300)
t = t.rotated(by: CGFloat.pi / 4)
t = t.scaledBy(x: -1, y: 2)
// ... add as many as you want, then apply it to to the view
imageView.transform = t

Or more compactly (but not necessarily as readable):

或者更简洁（但不一定可读）：

imageView.transform = CGAffineTransform.identity.translatedBy(x: 100, y: 300).rotated(by: CGFloat.pi / 4).scaledBy(x: -1, y: 2)

This series of transforms produces the image on the right:

这一系列的变换产生了右边的图像：

Thanks to this answerfor teaching me how to do it.

感谢这个答案教我如何去做。

Notes

笔记

• The order in which you apply the transforms matters. For example, if the transforms were done in the opposite order it would produce the following result.

  t = t.scaledBy(x: -1, y: 2)
  t = t.rotated(by: CGFloat.pi / 4)
  t = t.translatedBy(x: 100, y: 300)
  

• 应用转换的顺序很重要。例如，如果以相反的顺序进行转换，则会产生以下结果。

  t = t.scaledBy(x: -1, y: 2)
  t = t.rotated(by: CGFloat.pi / 4)
  t = t.translatedBy(x: 100, y: 300)
  

See also

也可以看看

• CGAffineTransform Reference(docs)
• Transforms(docs)
• Swift: Translating and Rotating a CGContext, A Visual Explanation (iOS/Xcode)
• Demystifying CGAffineTransform

• CGAffineTransform 参考（文档）
• 转换（文档）
• Swift：翻译和旋转 CGContext，一个视觉解释 (iOS/Xcode)
• 揭秘 CGAffineTransform

This answer has been tested with Swift 4

这个答案已经用 Swift 4 测试过

回答by Tyler Sheaffer

In Swift 3, these have been replaced by functions on CGAffineTransform itself, which can be chained.

在 Swift 3 中，这些已经被 CGAffineTransform 本身的函数所取代，它们可以被链接。

extension CGAffineTransform {
    public func translatedBy(x tx: CGFloat, y ty: CGFloat) -> CGAffineTransform
    public func scaledBy(x sx: CGFloat, y sy: CGFloat) -> CGAffineTransform
    public func rotated(by angle: CGFloat) -> CGAffineTransform
}

so for example

所以例如

let transform = CGAffineTransform(scaleX: 1.0, y: 3.0).translatedBy(x: 12, y: 9).rotated(by: 17.0)