private static double CompareCmc1984(ColorSpace color1, ColorSpace color2)
{
const double defaultLightness = 2.0;
const double defaultChroma = 1.0;
var lab1 = color1.ToColorSpace <Lab>();
var lab2 = color2.ToColorSpace <Lab>();
var deltaL = lab1.L - lab2.L;
var h = System.Math.Atan2(lab1.B, lab1.A);
var c1 = System.Math.Sqrt(lab1.A * lab1.A + lab1.B * lab1.B);
var c2 = System.Math.Sqrt(lab2.A * lab2.A + lab2.B * lab2.B);
var c1A = System.Math.Pow(c1, 4);
var deltaC = c1 - c2;
var deltaH = System.Math.Sqrt(
(lab1.A - lab2.A) * (lab1.A - lab2.A) + (lab1.B - lab2.B) * (lab1.B - lab2.B) - deltaC * deltaC);
var t = 164 <= h || h >= 345
? 0.56 + System.Math.Abs(0.2 * System.Math.Cos(h + 168.0))
: 0.36 + System.Math.Abs(0.4 * System.Math.Cos(h + 35.0));
var f = System.Math.Sqrt(c1A / (c1A + 1900.0));
var sL = lab1.L < 16 ? 0.511 : 0.040975 * lab1.L / (1.0 + 0.01765 * lab1.L);
var sC = 0.0638 * c1 / (1.0 + 0.0131 * c1) + 0.638;
var sH = sC * (f * t + 1.0 - f);
var diff = System.Math.Pow(deltaL / (defaultLightness * sL), 2) + System.Math.Pow(deltaC / (defaultChroma * sC), 2) +
System.Math.Pow(deltaH / sH, 2);
return(System.Math.Sqrt(diff));
}
private static double CompareCie1994(ColorSpace color1, ColorSpace color2)
{
const double kl = 1.0;
const double k1 = 0.045;
const double k2 = 0.015;
const double sl = 1.0;
const double kc = 1.0;
const double kh = 1.0;
var lab1 = color1.ToColorSpace <Lab>();
var lab2 = color2.ToColorSpace <Lab>();
var deltaL = lab1.L - lab2.L;
var deltaA = lab1.A - lab2.A;
var deltaB = lab1.B - lab2.B;
var c1 = System.Math.Sqrt(lab1.A * lab1.A + lab1.B * lab1.B);
var c2 = System.Math.Sqrt(lab2.A * lab2.A + lab2.B * lab2.B);
var deltaC = c1 - c2;
var deltaH = deltaA * deltaA + deltaB * deltaB - deltaC * deltaC;
deltaH = deltaH < 0 ? 0 : System.Math.Sqrt(deltaH);
var sc = 1.0 + k1 * c1;
var sh = 1.0 + k2 * c1;
var deltaL1 = deltaL / (kl * sl);
var deltaC1 = deltaC / (kc * sc);
var deltaH1 = deltaH / (kh * sh);
var i = deltaL1 * deltaL1 + deltaC1 * deltaC1 + deltaH1 * deltaH1;
return(i < 0 ? 0 : System.Math.Sqrt(i));
}
private static double CompareCie1976(ColorSpace color1, ColorSpace color2)
{
var lab1 = color1.ToColorSpace <Lab>();
var lab2 = color2.ToColorSpace <Lab>();
var diff = (lab1.L - lab2.L) * (lab1.L - lab2.L) + (lab1.A - lab2.A) * (lab1.A - lab2.A) +
(lab1.B - lab2.B) * (lab1.B - lab2.B);
return(System.Math.Sqrt(diff));
}
private static double CompareCie2000(ColorSpace color1, ColorSpace color2)
{
const double kl = 1.0;
const double kc = 1.0;
const double kh = 1.0;
var lab1 = color1.ToColorSpace <Lab>();
var lab2 = color2.ToColorSpace <Lab>();
var lBar = (lab1.L + lab2.L) / 2.0;
var c1 = System.Math.Sqrt(lab1.A * lab1.A + lab1.B * lab1.B);
var c2 = System.Math.Sqrt(lab2.A * lab2.A + lab2.B * lab2.B);
var cBar = (c1 + c2) / 2.0;
var cBarInPower7 = cBar * cBar * cBar;
cBarInPower7 *= cBarInPower7 * cBar;
var g = 1 - System.Math.Sqrt(cBarInPower7 / (cBarInPower7 + 6103515625));
var aPrime1 = lab1.A + lab1.A / 2.0 * g;
var aPrime2 = lab2.A + lab2.A / 2.0 * g;
var cPrime1 = System.Math.Sqrt(aPrime1 * aPrime1 + lab1.B * lab1.B);
var cPrime2 = System.Math.Sqrt(aPrime2 * aPrime2 + lab2.B * lab2.B);
var cBarPrime = (cPrime1 + cPrime2) / 2.0;
var hPrime1 = System.Math.Atan2(lab1.B, aPrime1) % 360;
var hPrime2 = System.Math.Atan2(lab2.B, aPrime2) % 360;
var hBar = System.Math.Abs(hPrime1 - hPrime2);
double deltaHPrime;
if (hBar <= 180)
{
deltaHPrime = hPrime2 - hPrime1;
}
else if (hBar > 180 && hPrime2 <= hPrime1)
{
deltaHPrime = hPrime2 - hPrime1 + 360.0;
}
else
{
deltaHPrime = hPrime2 - hPrime1 - 360.0;
}
var deltaLPrime = lab2.L - lab1.L;
var deltaCPrime = cPrime2 - cPrime1;
deltaHPrime = 2 * System.Math.Sqrt(cPrime1 * cPrime2) * System.Math.Sin(deltaHPrime / 2.0);
var hBarPrime = hBar > 180 ? (hPrime1 + hPrime2 + 360) / 2.0 : (hPrime1 + hPrime2) / 2.0;
var t = 1 - .17 * System.Math.Cos(hBarPrime - 30) + .24 * System.Math.Cos(2 * hBarPrime) +
.32 * System.Math.Cos(3 * hBarPrime + 6) - .2 * System.Math.Cos(4 * hBarPrime - 63);
var lBarMinus50Sqr = (lBar - 50) * (lBar - 50);
var sl = 1 + .015 * lBarMinus50Sqr / System.Math.Sqrt(20 + lBarMinus50Sqr);
var sc = 1 + .045 * cBarPrime;
var sh = 1 + .015 * cBarPrime * t;
var cBarPrimeInPower7 = cBarPrime * cBarPrime * cBarPrime;
cBarPrimeInPower7 *= cBarPrimeInPower7 * cBarPrime;
var rt = -2 * System.Math.Sqrt(cBarPrimeInPower7 / (cBarPrimeInPower7 + 6103515625)) // 25 ^ 7
* System.Math.Sin(60.0 * System.Math.Exp(-((hBarPrime - 275.0) / 25.0)));
var deltaLPrimeDivklsl = deltaLPrime / (kl * sl);
var deltaCPrimeDivkcsc = deltaCPrime / (kc * sc);
var deltaHPrimeDivkhsh = deltaHPrime / (kh * sh);
var deltaE = System.Math.Sqrt(
deltaLPrimeDivklsl * deltaLPrimeDivklsl + deltaCPrimeDivkcsc * deltaCPrimeDivkcsc +
deltaHPrimeDivkhsh * deltaHPrimeDivkhsh + rt * (deltaCPrime / (kc * kh)) * (deltaHPrime / (kh * sh)));
return(deltaE);
}
