AS3:获取 Matrix 对象的比例 [英] AS3: Getting the scale of a Matrix object

问题描述

大多数情况下，会询问有关如何缩放 DisplayObject 的问题，答案通常是使用矩阵.

Most often, questions are asked about how to scale a DisplayObject, and the answer is usually to use a Matrix.

我的问题是，如何获得矩阵的尺度(scaleX 和 scaleY)?

My question is, how to you GET the scale of a Matrix (scaleX and scaleY)?

有一个 Matrix.scale 方法来设置 scaleX 和 scaleY，但它不返回值，并且不存在其他属性来读取它.

There's a Matrix.scale method to set the scaleX and scaleY, but it doesn't return a value, and no other properties exist to read it back.

我问的原因是，我正在使用深埋在显示列表中的对象，每个对象都可能被转换.所以我使用了子对象的 sprite.transform.concatenatedMatrix getter，但在这一点上我不知道如何从中读取比例.

The reason I ask, I'm using object burried deep down into a Display list, and each may be transformed. So I use the child object's sprite.transform.concatenatedMatrix getter, but am stuck at this point on how to read the scale from it.

家里有数学奇才吗?

推荐答案

通常，隔离矩阵中缩放分量的可靠​​方法是使用所讨论的矩阵沿轴变换单位向量，然后测量结果向量的长度.

Generally, a reliable way to isolate the scaling component in a matrix is to use the matrix in question to transform the unit vectors along the axes, and then measure the length of the resulting vectors.

例如，给定来自 DisplayObject 的 transform，并使用 Matrix3D，将按如下方式获得 scaleX:

For instance, given the transform from a DisplayObject, and using the Matrix3D, the scaleX would be obtained as follows:

transform.matrix3D.deltaTransformVector(Vector3D.X_AXIS).length

或者，如果您使用连接的 2D 矩阵，scaleY 将是:

Or, if you use the concatenated 2D Matrix, the scaleY would be:

transform.concatenatedMatrix.deltaTransformPoint(new Point(0,1)).length

请注意，deltaTransform* 函数忽略了矩阵的平移效果，这对缩放没有影响.

Note that the deltaTransform* functions ignore the translation effects of the matrices, which have no effect on the scaling.

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