internal static LchColor LabToLch(LabColor lab)
{
var c = Math.Sqrt(lab.A * lab.A + lab.B * lab.B);
var h = (Math.Atan2(lab.B, lab.A) * (180 / Math.PI) + 360) % 360;
if (Math.Round(c * 10000) == 0)
{
h = double.NaN;
}
return(new LchColor(lab.L, c, h));
}
internal static Color LabToRgb(LabColor lab)
{
Func <double, double> xyz_rgb = (t) =>
{
return(255 * (t <= 0.00304 ? 12.92 * t : 1.055 * Math.Pow(t, 1 / 2.4) - 0.055));
};
Func <double, double> lab_xyz = (t) =>
{
if (t > LabColor.LabConstants.T1)
{
return(t * t * t);
}
else
{
return(LabColor.LabConstants.T2 * (t - LabColor.LabConstants.T0));
}
};
double a, b, g, l, r, x, y, z;
l = lab.L;
a = lab.A;
b = lab.B;
y = (l + 16) / 116;
x = double.IsNaN(a) ? y : y + a / 500;
z = double.IsNaN(b) ? y : y - b / 200;
y = LabColor.LabConstants.Yn * lab_xyz(y);
x = LabColor.LabConstants.Xn * lab_xyz(x);
z = LabColor.LabConstants.Zn * lab_xyz(z);
r = xyz_rgb(3.2404542 * x - 1.5371385 * y - 0.4985314 * z);
g = xyz_rgb(-0.9692660 * x + 1.8760108 * y + 0.0415560 * z);
b = xyz_rgb(0.0556434 * x - 0.2040259 * y + 1.0572252 * z);
return(new Color(Convert.ToInt32(r), Convert.ToInt32(g), Convert.ToInt32(b), lab.Alpha));
}
