public static double Calc76(LAB lab1, LAB lab2)
{
var lDiff = Math.Pow(lab2.l - lab1.l, 2);
var aDiff = Math.Pow(lab2.a - lab1.a, 2);
var bDiff = Math.Pow(lab2.b - lab1.b, 2);
var delta76 = Math.Sqrt(lDiff + aDiff + bDiff);
return(delta76);
}
/*
* CIE94 implemtation was lifted almost verbatim from Shaun Lynch's blog:
* https://blog.genreof.com/post/comparing-colors-using-delta-e-1994-in-c
*/
public static double Calc94(LAB lab1, LAB lab2)
{
double k1 = 0.045; // 0.045 graphic arts, 0.048 textiles
double k2 = 0.015; // 0.015 graphic arts, 0.014 textiles
double kl = 1; // 1 default, 2 textiles
double kc = 1;
double kh = 1;
double xc1 = Math.Sqrt(Math.Pow(lab1.a, 2) + Math.Pow(lab1.b, 2));
double xc2 = Math.Sqrt(Math.Pow(lab2.a, 2) + Math.Pow(lab2.b, 2));
double sl = 1;
double sc = 1 + k1 * xc1;
double sh = 1 + k2 * xc1;
double delta_L = lab1.l - lab2.l;
double delta_C = xc1 - xc2;
double delta_a = lab1.a - lab2.a;
double delta_b = lab1.b - lab2.b;
double delta_H = 0;
double deltaHCalc = Math.Pow(delta_a, 2) + Math.Pow(delta_b, 2) - Math.Pow(delta_C, 2);
// Can't do a sqrt of a negative num
if (deltaHCalc < 0)
{
delta_H = 0;
}
else
{
delta_H = Math.Sqrt(deltaHCalc);
}
// Make double sure that delta_H is non-negative
if (double.IsNaN(delta_H) || delta_H < 0)
{
delta_H = 0;
}
double lgroup = Math.Pow(delta_L / (kl * sl), 2);
double cgroup = Math.Pow(delta_C / (kc * sc), 2);
double hgroup = Math.Pow(delta_H / (kh * sh), 2);
double delta94 = Math.Sqrt(lgroup + cgroup + hgroup);
return(delta94);
}
/*
* CIE2000 ported from Greg Fiumara's C++ implementation:
* https://github.com/gfiumara/CIEDE2000
*/
public static double Calc2000(LAB lab1, LAB lab2)
{
double k_L = 1.0;
double k_C = 1.0;
double k_H = 1.0;
double deg360InRad = deg2Rad(360.0);
double deg180InRad = deg2Rad(180.0);
double pow25To7 = 6103515625.0; /* pow(25, 7) */
/*
* Step 1
*/
/* Equation 2 */
double C1 = Math.Sqrt((lab1.a * lab1.a) + (lab1.b * lab1.b));
double C2 = Math.Sqrt((lab2.a * lab2.a) + (lab2.b * lab2.b));
/* Equation 3 */
double barC = (C1 + C2) / 2.0;
/* Equation 4 */
double G = 0.5 * (1 - Math.Sqrt(Math.Pow(barC, 7) / (Math.Pow(barC, 7) + pow25To7)));
/* Equation 5 */
double a1Prime = (1.0 + G) * lab1.a;
double a2Prime = (1.0 + G) * lab2.a;
/* Equation 6 */
double CPrime1 = Math.Sqrt((a1Prime * a1Prime) + (lab1.b * lab1.b));
double CPrime2 = Math.Sqrt((a2Prime * a2Prime) + (lab2.b * lab2.b));
/* Equation 7 */
double hPrime1;
if (lab1.b == 0 && a1Prime == 0)
{
hPrime1 = 0.0;
}
else
{
hPrime1 = Math.Atan2(lab1.b, a1Prime);
/*
* This must be converted to a hue angle in degrees between 0
* and 360 by addition of 2 to negative hue angles.
*/
if (hPrime1 < 0)
{
hPrime1 += deg360InRad;
}
}
double hPrime2;
if (lab2.b == 0 && a2Prime == 0)
{
hPrime2 = 0.0;
}
else
{
hPrime2 = Math.Atan2(lab2.b, a2Prime);
/*
* This must be converted to a hue angle in degrees between 0
* and 360 by addition of 2 to negative hue angles.
*/
if (hPrime2 < 0)
{
hPrime2 += deg360InRad;
}
}
/*
* Step 2
*/
/* Equation 8 */
double deltaLPrime = lab2.l - lab1.l;
/* Equation 9 */
double deltaCPrime = CPrime2 - CPrime1;
/* Equation 10 */
double deltahPrime;
double CPrimeProduct = CPrime1 * CPrime2;
if (CPrimeProduct == 0)
{
deltahPrime = 0;
}
else
{
/* Avoid the fabs() call */
deltahPrime = hPrime2 - hPrime1;
if (deltahPrime < -deg180InRad)
{
deltahPrime += deg360InRad;
}
else if (deltahPrime > deg180InRad)
{
deltahPrime -= deg360InRad;
}
}
/* Equation 11 */
double deltaHPrime = 2.0 * Math.Sqrt(CPrimeProduct) *
Math.Sin(deltahPrime / 2.0);
/*
* Step 3
*/
/* Equation 12 */
double barLPrime = (lab1.l + lab2.l) / 2.0;
/* Equation 13 */
double barCPrime = (CPrime1 + CPrime2) / 2.0;
/* Equation 14 */
double barhPrime, hPrimeSum = hPrime1 + hPrime2;
if (CPrime1 * CPrime2 == 0)
{
barhPrime = hPrimeSum;
}
else
{
if (Math.Abs(hPrime1 - hPrime2) <= deg180InRad)
{
barhPrime = hPrimeSum / 2.0;
}
else
{
if (hPrimeSum < deg360InRad)
{
barhPrime = (hPrimeSum + deg360InRad) / 2.0;
}
else
{
barhPrime = (hPrimeSum - deg360InRad) / 2.0;
}
}
}
/* Equation 15 */
double T = 1.0 - (0.17 * Math.Cos(barhPrime - deg2Rad(30.0))) +
(0.24 * Math.Cos(2.0 * barhPrime)) +
(0.32 * Math.Cos((3.0 * barhPrime) + deg2Rad(6.0))) -
(0.20 * Math.Cos((4.0 * barhPrime) - deg2Rad(63.0)));
/* Equation 16 */
double deltaTheta = deg2Rad(30.0) *
Math.Exp(-1 * (Math.Pow((barhPrime - deg2Rad(275.0)) / deg2Rad(25.0), 2.0)));
/* Equation 17 */
double R_C = 2.0 * Math.Sqrt(Math.Pow(barCPrime, 7.0) /
(Math.Pow(barCPrime, 7.0) + pow25To7));
/* Equation 18 */
double S_L = 1 + ((0.015 * Math.Pow(barLPrime - 50.0, 2.0)) /
Math.Sqrt(20 + Math.Pow(barLPrime - 50.0, 2.0)));
/* Equation 19 */
double S_C = 1 + (0.045 * barCPrime);
/* Equation 20 */
double S_H = 1 + (0.015 * barCPrime * T);
/* Equation 21 */
double R_T = (-1 * (Math.Sin(2.0 * deltaTheta))) * R_C;
/* Equation 22 */
double deltaE = Math.Sqrt(
Math.Pow(deltaLPrime / (k_L * S_L), 2.0) +
Math.Pow(deltaCPrime / (k_C * S_C), 2.0) +
Math.Pow(deltaHPrime / (k_H * S_H), 2.0) +
(R_T * (deltaCPrime / (k_C * S_C)) * (deltaHPrime / (k_H * S_H))));
return(deltaE);
}
