/// <summary>
/// Converts CIEXYZ to CIELab structure.
/// </summary>
public static CIELab XYZtoLab(double x, double y, double z)
{
CIELab lab = CIELab.Empty;
lab.L = 116.0 * Fxyz(y / CIEXYZ.D65.Y) - 16;
lab.A = 500.0 * (Fxyz(x / CIEXYZ.D65.X) - Fxyz(y / CIEXYZ.D65.Y));
lab.B = 200.0 * (Fxyz(y / CIEXYZ.D65.Y) - Fxyz(z / CIEXYZ.D65.Z));
return(lab);
}
// ******************************************************************
// EO: Based on: http://www.easyrgb.com/index.php?X=DELT&H=04#text4
// Based on: Delta E 1994
public static double GetDistanceBetweenCie1994(CIELab lab1, CIELab lab2)
{
const double whtL = 1;
const double whtC = 1;
const double whtH = 1; //Weighting factors depending
//on the application (1 = default)
double xC1 = Math.Sqrt(Math.Pow(lab1.a, 2.0) + Math.Pow(lab1.b, 2.0));
double xC2 = Math.Sqrt(Math.Pow(lab2.a, 2.0) + Math.Pow(lab2.b, 2.0));
double xDL = lab2.l - lab1.l;
double xDC = xC2 - xC1;
double xDE = Math.Sqrt(
((lab1.l - lab2.l) * (lab1.l - lab2.l))
+ ((lab1.a - lab2.a) * (lab1.a - lab2.a))
+ ((lab1.b - lab2.b) * (lab1.b - lab2.b)));
double xDH;
if (Math.Sqrt(xDE) > (Math.Sqrt(Math.Abs(xDL)) + Math.Sqrt(Math.Abs(xDC))))
{
xDH = Math.Sqrt((xDE * xDE) - (xDL * xDL) - (xDC * xDC));
}
else
{
xDH = 0;
}
double xSC = 1 + (0.045 * xC1);
double xSH = 1 + (0.015 * xC1);
xDL /= whtL;
xDC /= whtC * xSC;
xDH /= whtH * xSH;
double deltaE94 = Math.Sqrt(Math.Pow(xDL, 2.0) + Math.Pow(xDC, 2.0) + Math.Pow(xDH, 2.0));
return(deltaE94);
}
/// <summary>
/// Gets the "distance" between two colors calculated with CIELab algo
/// </summary>
/// EO Added 2011-09-08
/// <param name="color1">First color.</param>
/// <param name="color2">Second color.</param>
public static double GetColorDistanceCIELab(Color c1, Color c2)
{
return(CIELab.GetDistanceBetweenCie2000(RGBtoLab(c1), RGBtoLab(c2)));
}
/// <summary>
/// Converts CIELab to RGB.
/// </summary>
public static RGB LabtoRGB(CIELab lab)
{
return(XYZtoRGB(LabtoXYZ(lab)));
}
/// <summary>
/// Converts CIELab to CIEXYZ.
/// </summary>
public static CIEXYZ LabtoXYZ(CIELab lab)
{
return(LabtoXYZ(lab.L, lab.A, lab.B));
}
/// <summary>
/// Converts CIELab to CIEXYZ.
/// </summary>
public static CIEXYZ LabtoXYZ(CIELab lab)
{
return LabtoXYZ(lab.L, lab.A, lab.B);
}
/// <summary>
/// Converts CIELab to RGB.
/// </summary>
public static RGB LabtoRGB(CIELab lab)
{
return XYZtoRGB(LabtoXYZ(lab));
}
// ******************************************************************
// Given by Rob2412 http://www.codeproject.com/KB/recipes/colorspace1.aspx?msg=4041550#xx4041550xx
// and should be better then the previous one.
/// <summary>
/// Returns the color difference (distance) between a sample color CIELap(2) and a reference color CIELap(1)
/// <para>in accorance with CIE 2000 alogorithm.</para>
/// </summary>
/// <param name="lab1">CIELap reference color.</param>
/// <param name="lab2">CIELap sample color.</param>
/// <returns>Color difference.</returns>
public static double GetDistanceBetweenCie2000(CIELab lab1, CIELab lab2)
{
double p25 = Math.Pow(25, 7);
double C1 = Math.Sqrt(lab1.A * lab1.A + lab1.B * lab1.B);
double C2 = Math.Sqrt(lab2.A * lab2.A + lab2.B * lab2.B);
double avgC = (C1 + C2) / 2F;
double powAvgC = Math.Pow(avgC, 7);
double G = (1 - Math.Sqrt(powAvgC / (powAvgC + p25))) / 2D;
double a_1 = lab1.A * (1 + G);
double a_2 = lab2.A * (1 + G);
double C_1 = Math.Sqrt(a_1 * a_1 + lab1.B * lab1.B);
double C_2 = Math.Sqrt(a_2 * a_2 + lab2.B * lab2.B);
double avgC_ = (C_1 + C_2) / 2D;
double h1 = (Atan(lab1.B, a_1) >= 0 ? Atan(lab1.B, a_1) : Atan(lab1.B, a_1) + 360F);
double h2 = (Atan(lab2.B, a_2) >= 0 ? Atan(lab2.B, a_2) : Atan(lab2.B, a_2) + 360F);
double H = (h1 - h2 > 180D ? (h1 + h2 + 360F) / 2D : (h1 + h2) / 2D);
double T = 1;
T -= 0.17 * Cos(H - 30);
T += 0.24 * Cos(2 * H);
T += 0.32 * Cos(3 * H + 6);
T -= 0.20 * Cos(4 * H - 63);
double deltah = 0;
if (h2 - h1 <= 180)
deltah = h2 - h1;
else if (h2 <= h1)
deltah = h2 - h1 + 360;
else
deltah = h2 - h1 - 360;
double avgL = (lab1.L + lab2.L) / 2F;
double deltaL_ = lab2.L - lab1.L;
double deltaC_ = C_2 - C_1;
double deltaH_ = 2 * Math.Sqrt(C_1 * C_2) * Sin(deltah / 2);
double SL = 1 + (0.015 * Math.Pow(avgL - 50, 2)) / Math.Sqrt(20 + Math.Pow(avgL - 50, 2));
double SC = 1 + 0.045 * avgC_;
double SH = 1 + 0.015 * avgC_ * T;
double exp = Math.Pow((H - 275) / 25, 2);
double teta = Math.Pow(30, -exp);
double RC = 2D * Math.Sqrt(Math.Pow(avgC_, 7) / (Math.Pow(avgC_, 7) + p25));
double RT = -RC * Sin(2 * teta);
double deltaE = 0;
deltaE = Math.Pow(deltaL_ / SL, 2);
deltaE += Math.Pow(deltaC_ / SC, 2);
deltaE += Math.Pow(deltaH_ / SH, 2);
deltaE += RT * (deltaC_ / SC) * (deltaH_ / SH);
deltaE = Math.Sqrt(deltaE);
return deltaE;
}
// ******************************************************************
// EO: Based on: http://www.easyrgb.com/index.php?X=DELT&H=04#text4
// Based on: Delta E 1994
public static double GetDistanceBetweenCie1994(CIELab lab1, CIELab lab2)
{
const double whtL = 1;
const double whtC = 1;
const double whtH = 1; //Weighting factors depending
//on the application (1 = default)
double xC1 = Math.Sqrt(Math.Pow(lab1.a, 2.0) + Math.Pow(lab1.b, 2.0));
double xC2 = Math.Sqrt(Math.Pow(lab2.a, 2.0) + Math.Pow(lab2.b, 2.0));
double xDL = lab2.l - lab1.l;
double xDC = xC2 - xC1;
double xDE = Math.Sqrt(
((lab1.l - lab2.l) * (lab1.l - lab2.l))
+ ((lab1.a - lab2.a) * (lab1.a - lab2.a))
+ ((lab1.b - lab2.b) * (lab1.b - lab2.b)));
double xDH;
if (Math.Sqrt( xDE ) > ( Math.Sqrt( Math.Abs( xDL ) ) + Math.Sqrt( Math.Abs( xDC ) ) ) )
{
xDH = Math.Sqrt((xDE*xDE) - (xDL*xDL) - (xDC*xDC));
}
else
{
xDH = 0;
}
double xSC = 1 + (0.045*xC1);
double xSH = 1 + (0.015*xC1);
xDL /= whtL;
xDC /= whtC*xSC;
xDH /= whtH*xSH;
double deltaE94 = Math.Sqrt(Math.Pow(xDL, 2.0) + Math.Pow(xDC, 2.0) + Math.Pow(xDH, 2.0));
return deltaE94;
}
// ******************************************************************
// Given by Rob2412 http://www.codeproject.com/KB/recipes/colorspace1.aspx?msg=4041550#xx4041550xx
// and should be better then the previous one.
/// <summary>
/// Returns the color difference (distance) between a sample color CIELap(2) and a reference color CIELap(1)
/// <para>in accorance with CIE 2000 alogorithm.</para>
/// </summary>
/// <param name="lab1">CIELap reference color.</param>
/// <param name="lab2">CIELap sample color.</param>
/// <returns>Color difference.</returns>
public static double GetDistanceBetweenCie2000(CIELab lab1, CIELab lab2)
{
double p25 = Math.Pow(25, 7);
double C1 = Math.Sqrt(lab1.A * lab1.A + lab1.B * lab1.B);
double C2 = Math.Sqrt(lab2.A * lab2.A + lab2.B * lab2.B);
double avgC = (C1 + C2) / 2F;
double powAvgC = Math.Pow(avgC, 7);
double G = (1 - Math.Sqrt(powAvgC / (powAvgC + p25))) / 2D;
double a_1 = lab1.A * (1 + G);
double a_2 = lab2.A * (1 + G);
double C_1 = Math.Sqrt(a_1 * a_1 + lab1.B * lab1.B);
double C_2 = Math.Sqrt(a_2 * a_2 + lab2.B * lab2.B);
double avgC_ = (C_1 + C_2) / 2D;
double h1 = (Atan(lab1.B, a_1) >= 0 ? Atan(lab1.B, a_1) : Atan(lab1.B, a_1) + 360F);
double h2 = (Atan(lab2.B, a_2) >= 0 ? Atan(lab2.B, a_2) : Atan(lab2.B, a_2) + 360F);
double H = (h1 - h2 > 180D ? (h1 + h2 + 360F) / 2D : (h1 + h2) / 2D);
double T = 1;
T -= 0.17 * Cos(H - 30);
T += 0.24 * Cos(2 * H);
T += 0.32 * Cos(3 * H + 6);
T -= 0.20 * Cos(4 * H - 63);
double deltah = 0;
if (h2 - h1 <= 180)
{
deltah = h2 - h1;
}
else if (h2 <= h1)
{
deltah = h2 - h1 + 360;
}
else
{
deltah = h2 - h1 - 360;
}
double avgL = (lab1.L + lab2.L) / 2F;
double deltaL_ = lab2.L - lab1.L;
double deltaC_ = C_2 - C_1;
double deltaH_ = 2 * Math.Sqrt(C_1 * C_2) * Sin(deltah / 2);
double SL = 1 + (0.015 * Math.Pow(avgL - 50, 2)) / Math.Sqrt(20 + Math.Pow(avgL - 50, 2));
double SC = 1 + 0.045 * avgC_;
double SH = 1 + 0.015 * avgC_ * T;
double exp = Math.Pow((H - 275) / 25, 2);
double teta = Math.Pow(30, -exp);
double RC = 2D * Math.Sqrt(Math.Pow(avgC_, 7) / (Math.Pow(avgC_, 7) + p25));
double RT = -RC *Sin(2 *teta);
double deltaE = 0;
deltaE = Math.Pow(deltaL_ / SL, 2);
deltaE += Math.Pow(deltaC_ / SC, 2);
deltaE += Math.Pow(deltaH_ / SH, 2);
deltaE += RT * (deltaC_ / SC) * (deltaH_ / SH);
deltaE = Math.Sqrt(deltaE);
return(deltaE);
}
