public static void Decompose(Matrix2 m, out float scaleX, out float scaleY, out float shearXY,
out float rot)
{
Matrix2 mtx = m;
scaleX = Point.Length(mtx[0]) * Matrix2.Sign(mtx[0][0]);
mtx[0] = mtx[0] / scaleX;
shearXY = Point.Dot(mtx[0], mtx[1]);
mtx[1] -= mtx[0] * shearXY;
scaleY = Point.Length(mtx[1]) * Matrix2.Sign(mtx[1][1]);
mtx[1] = mtx[1] / scaleY;
shearXY /= scaleY;
rot = (float)Math.Atan2(-mtx[1][0], mtx[1][1]);
}
public void SetUpper2x2(Matrix2 m)
{
this[0] = m[0];
this[1] = m[1];
}
public static Matrix2 PreScale(float scaleX, float scaleY, Matrix2 m)
{
return(new Matrix2(m[0][0] * scaleX, m[0][1] * scaleX, m[1][0] * scaleY, m[1][1] * scaleY));
}
public static Matrix2 PostScale(Matrix2 m, float scaleX, float scaleY)
{
return(new Matrix2(m[0][0] * scaleX, m[0][1] * scaleY, m[1][0] * scaleX, m[1][1] * scaleY));
}
public static Matrix2 Inverse(Matrix2 m, float determinant)
{
return(new Matrix2(m[1][1], -m[0][1], -m[1][0], m[0][0]) / determinant);
}
public static Matrix2 Inverse(Matrix2 m)
{
return(Inverse(m, Determinant(m)));
}
public static float Determinant(Matrix2 m)
{
return(m[0][0] * m[1][1] - m[0][1] * m[1][0]);
}
public static Matrix2 Transpose(Matrix2 m)
{
return(new Matrix2(m[0][0], m[1][0], m[0][1], m[1][1]));
}
public bool Equals(Matrix2 m)
{
return(this == m);
}