internal class ColorDifferences
{
/// <CIE 1976 L*a*b*色差公式>
/// </summary>
/// <param name="L1"></param>
/// <param name="a1"></param>
/// <param name="b1"></param>
/// <param name="L2"></param>
/// <param name="a2"></param>
/// <param name="b2"></param>
/// <returns></returns>
public static double delta_Eab(double L1, double a1, double b1, double L2, double a2, double b2)
{
double Eab = 0; // △Eab
double chafang_L = 0; // (L1-L2)*(L1-L2)
double chafang_a = 0; // (a1-a2)*(a1-a2)
double chafang_b = 0; // (b1-b2)*(b1-b2)
chafang_L = ( L1 - L2 ) * ( L1 - L2 ); //差-方
chafang_a = ( a1 - a2 ) * ( a1 - a2 );
chafang_b = ( b1 - b2 ) * ( b1 - b2 );
Eab = Math.Pow(chafang_L + chafang_a + chafang_b, 0.5);
return Eab;
}
/// <CIE DE 2000色差公式>
/// </summary>
/// <param name="L1"></param>
/// <param name="a1"></param>
/// <param name="b1"></param>
/// <param name="L2"></param>
/// <param name="a2"></param>
/// <param name="b2"></param>
/// <returns></returns>
public static double delta_E00(double L1, double a1, double b1, double L2, double a2, double b2)
{
//参考《现代颜色技术原理及应用》P88数据
double E00 = 0; //CIEDE2000色差E00
double LL1, LL2, aa1, aa2, bb1, bb2; //声明L' a' b' (1,2)
double delta_LL, delta_CC, delta_hh, delta_HH; // 第二部的四个量
double kL, kC, kH;
double RT = 0; //旋转函数RT
double G = 0; //G表示CIELab 颜色空间a轴的调整因子,是彩度的函数.
double mean_Cab = 0; //两个样品彩度的算术平均值
double SL, SC, SH, T;
//------------------------------------------
//参考实验条件见P88
kL = 1;
kC = 1;
kH = 1;
//------------------------------------------
mean_Cab = (CaiDu(a1, b1) + CaiDu(a2, b2)) / 2;
double mean_Cab_pow7 = Math.Pow(mean_Cab, 7); //两彩度平均值的7次方
G = 0.5*(1-Math.Pow(mean_Cab_pow7 / (mean_Cab_pow7 + Math.Pow(25, 7)), 0.5));
LL1 = L1;
aa1 = a1 * (1 + G);
bb1 = b1;
LL2 = L2;
aa2 = a2 * (1 + G);
bb2 = b2;
double CC1, CC2; //两样本的彩度值
CC1 = CaiDu(aa1, bb1);
CC2 = CaiDu(aa2, bb2);
double hh1, hh2; //两样本的色调角
hh1 = SeDiaoJiao(aa1, bb1);
hh2 = SeDiaoJiao(aa2, bb2);
delta_LL = LL1 - LL2;
delta_CC = CC1 - CC2;
delta_hh = SeDiaoJiao(aa1, bb1) - SeDiaoJiao(aa2, bb2);
delta_HH = 2 * Math.Sin(Math.PI*delta_hh / 360) * Math.Pow(CC1 * CC2, 0.5);
//-------第三步--------------
//计算公式中的加权函数SL,SC,SH,T
double mean_LL = (LL1 + LL2) / 2;
double mean_CC = (CC1 + CC2) / 2;
double mean_hh = (hh1 + hh2) / 2;
SL = 1 + 0.015 * Math.Pow(mean_LL - 50, 2) / Math.Pow(20 + Math.Pow(mean_LL - 50, 2), 0.5);
SC = 1 + 0.045 * mean_CC;
T = 1 - 0.17 * Math.Cos((mean_hh - 30) * Math.PI / 180) + 0.24 * Math.Cos((2 * mean_hh) * Math.PI / 180)
+ 0.32 * Math.Cos((3 * mean_hh + 6) * Math.PI / 180) - 0.2 * Math.Cos((4 * mean_hh - 63) * Math.PI / 180);
SH = 1 + 0.015 * mean_CC * T;
//------第四步--------
//计算公式中的RT
double mean_CC_pow7 = Math.Pow(mean_CC, 7);
double RC = 2 * Math.Pow(mean_CC_pow7 / (mean_CC_pow7 + Math.Pow(25, 7)), 0.5);
double delta_xita = 30 * Math.Exp(-Math.Pow((mean_hh - 275) / 25, 2)); //△θ 以°为单位
RT = -Math.Sin((2 * delta_xita) * Math.PI / 180) * RC;
double L_item, C_item, H_item;
L_item = delta_LL / (kL * SL);
C_item = delta_CC / (kC * SC);
H_item = delta_HH / (kH * SH);
E00 = Math.Pow(L_item * L_item + C_item * C_item + H_item * H_item + RT * C_item * H_item, 0.5);
return E00;
}
//彩度计算
private static double CaiDu(double a,double b)
{
double Cab = 0;
Cab = Math.Pow(a * a + b * b, 0.5);
return Cab;
}
//色调角计算
private static double SeDiaoJiao(double a, double b)
{
double h = 0;
double hab = 0;
h = (180 / Math.PI) * Math.Atan(b / a); //有正有负
if (a>0&;&;b>0)
{
hab = h;
}
else if (a<0&;&;b>0)
{
hab = 180 + h;
}
else if (a<0&;&;b<0)
{
hab = 180 + h;
}
else //a>0&;&;b<0
{
hab = 360 + h;
}
return hab;
}
}