找到矩阵变换的旋转和偏斜 [英] Find the Rotation and Skew of a Matrix transformation

问题描述

我在CSS中有以下转换矩阵

I have the the following Transform Matrix in CSS

// rotate the element 60deg
element.style.transform = "matrix(0.5,0.866025,-0.866025,0.5,0,0)"

and i可以使用这个来找到轮换......

And i can find the rotation using this...

// where a = [0.710138,0.502055,-0.57735,1,0,0]
var rotation = ((180/Math.PI) * Math.atan2( ((0*a[2])+(1*a[3])),((0*a[0])-(1*a[1]))) - 90
console.log(rotation); // ~60

类似于偏斜，如果......

Similarly for skew if...

// skew(30deg,-50deg) 
element.style.transform = "matrix(1,-1.19175,0.57735,1,0,0)"

var skewY = ((180/Math.PI) * Math.atan2( ((0*a[2])+(1*a[3])),((0*a[0])-(1*a[1]))) - 90;
var skewX = (180/Math.PI) * Math.atan2( ((1*a[2])+(0*a[3])),((1*a[0])-(0*a[1])));

console.log([skewX,skewY]); // ~= [30,-50] 

然而，只要我同时使用歪斜和旋转，一切都变得奇怪，尤其是因为th旋转公式与倾斜公式相同...因此公式不能正确。

However as soon as i use both skew and rotation everything goes weird not least because the formula for rotation is identical to that of skew... so the formulas can't be right.

我如何确定旋转和放大？两个属性都被应用的倾斜，我所知道的就是矩阵变换。

How do i determine both rotation & skew where both attributes have been applied and all i know is the Matrix Transform.

同样缩放我的偏斜值，我认为不应该这样。

Also scale messed up my skew values, which i dont think it should.

推荐答案

我需要相同的功能，今天我最终得到了这个非常好的代码。

I needed same functionality and today I ended up with this code that works very good.

我从这里获取灵感：
https://www.youtube.com/观看？v = 51MRHjKSbtk
并且来自下面的答案，没有提示 QR分解我永远找不到它

I took inspiration from here: https://www.youtube.com/watch?v=51MRHjKSbtk and from the answer below, without the hint QR decomposition i would never find it out

我在2x2案例中工作，我将尝试扩展到2x3以包含翻译。
但它应该很容易

I worked on a 2x2 case, i will try to expand to 2x3 to include also translations. But it should be easy

var a = [a, b, c, d, e, f];
var qrDecompone = function(a) {
  var angle = Math.atan2(a[1], a[0]),
      denom = Math.pow(a[0], 2) + Math.pow(a[1], 2),
      scaleX = Math.sqrt(denom),
      scaleY = (a[0] * a[3] - a[2] * a[1]) / scaleX,
      skewX = Math.atan2(a[0] * a[2] + a[1] * a[3], denom);
  return {
    angle: angle / (Math.PI / 180),  // this is rotation angle in degrees
    scaleX: scaleX,                  // scaleX factor  
    scaleY: scaleY,                  // scaleY factor
    skewX: skewX / (Math.PI / 180),  // skewX angle degrees
    skewY: 0,                        // skewY angle degrees
    translateX: a[4],                // translation point  x
    translateY: a[5]                 // translation point  y
  };
};

看起来，在分解之前，transformMatrix中的最后两个项是翻译值。你可以直接提取它们。

It looks like that the last two items in the transformMatrix, before decomposition, are translation values. You can extract them directly.

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