/// <summary>
/// Initializes a new instance of the <see cref="HueProcessor{TColor}"/> class.
/// </summary>
/// <param name="angle">The new brightness of the image. Must be between -100 and 100.</param>
public HueProcessor(float angle)
{
// Wrap the angle round at 360.
angle = angle % 360;
// Make sure it's not negative.
while (angle < 0)
{
angle += 360;
}
this.Angle = angle;
float radians = ImageMaths.DegreesToRadians(angle);
double cosradians = Math.Cos(radians);
double sinradians = Math.Sin(radians);
float lumR = .213f;
float lumG = .715f;
float lumB = .072f;
float oneMinusLumR = 1 - lumR;
float oneMinusLumG = 1 - lumG;
float oneMinusLumB = 1 - lumB;
// The matrix is set up to preserve the luminance of the image.
// See http://graficaobscura.com/matrix/index.html
// Number are taken from https://msdn.microsoft.com/en-us/library/jj192162(v=vs.85).aspx
Matrix4x4 matrix4X4 = new Matrix4x4()
{
M11 = (float)(lumR + (cosradians * oneMinusLumR) - (sinradians * lumR)),
M12 = (float)(lumR - (cosradians * lumR) - (sinradians * 0.143)),
M13 = (float)(lumR - (cosradians * lumR) - (sinradians * oneMinusLumR)),
M21 = (float)(lumG - (cosradians * lumG) - (sinradians * lumG)),
M22 = (float)(lumG + (cosradians * oneMinusLumG) + (sinradians * 0.140)),
M23 = (float)(lumG - (cosradians * lumG) + (sinradians * lumG)),
M31 = (float)(lumB - (cosradians * lumB) + (sinradians * oneMinusLumB)),
M32 = (float)(lumB - (cosradians * lumB) - (sinradians * 0.283)),
M33 = (float)(lumB + (cosradians * oneMinusLumB) + (sinradians * lumB)),
M44 = 1
};
this.Matrix = matrix4X4;
}
