static HueMatricies()
{
// Rotating the hue of an image is a rather convoluted task, involving several matrix
// multiplications. For efficiency, we prepare two static matrices.
// This is by far the most complicated part of this class. For the background
// theory, refer to the sgi-sites mentioned at the top of this file.
// Prepare the preHue matrix.
// Rotate the grey vector in the green plane.
PreHue.RotateRed(45.0f);
// Next, rotate it again in the green plane, so it coincides with the blue axis.
PreHue.RotateGreen(-greenRotation, MatrixOrder.Append);
// Hue rotations keep the color luminations constant, so that only the hues change
// visible. To accomplish that, we shear the blue plane.
var lum = PreHue.TransformVector(LuminanceRed, LuminanceGreen, LuminanceBlue, 1.0f);
// Transform the luminance vector.
// Calculate the shear factors for red and green.
float red = lum[0] / lum[2];
float green = lum[1] / lum[2];
// Shear the blue plane.
PreHue.ShearBlue(red, green, MatrixOrder.Append);
// Prepare the postHue matrix. This holds the opposite transformations of the
// preHue matrix. In fact, postHue is the inversion of preHue.
PostHue.ShearBlue(-red, -green);
PostHue.RotateGreen(greenRotation, MatrixOrder.Append);
PostHue.RotateRed(-45.0f, MatrixOrder.Append);
}
