/**
* Create viewing conditions assuming full adaption. This is primarily useful in color management
* applications.
*
* @param XYZ_w XYZ of adopted whitepoint
* @param L_A average luminance of visual surround
* @param Y_b adaptation luminance of color background
* @param sur the surrounding
* @return a fully adapted viewing conditions instance
*/
public static ViewingConditions createFullyAdapted(
CIEXYZ XYZ_w, float L_A, float Y_b, Surrounding sur) {
double[] xyz_w = MathTools.floatToDoubleArray(XYZ_w.toCIEXYZ100());
double[] RGB_w = CS_CIECAM02.XYZtoCAT02(xyz_w);
double[] RGB_c = calcAdaptedRGBc(XYZ_w, RGB_w, 1.0);
return new ViewingConditions(xyz_w, L_A, Y_b, sur, RGB_w, RGB_c);
}
/**
* Construct a new ViewingConditions instance. The degree of adaption (D) is derived from the
* background and surround. This is the standard case treated in CIE 159:2004.
*
* @param XYZ_w XYZ of adopted whitepoint
* @param L_A average luminance of visual surround
* @param Y_b adaptation luminance of color background
* @param sur the surrounding
* @return a ViewingConditions instance
*/
public static ViewingConditions createAdapted(
CIEXYZ XYZ_w, double L_A, double Y_b, Surrounding sur) {
double[] xyz_w = MathTools.floatToDoubleArray(XYZ_w.toCIEXYZ100());
// calculate RGB whitepoint
double[] RGB_w = CS_CIECAM02.XYZtoCAT02(xyz_w);
double D = calcD(L_A, sur);
double[] RGB_c = calcAdaptedRGBc(XYZ_w, RGB_w, D);
return new ViewingConditions(xyz_w, L_A, Y_b, sur, RGB_w, RGB_c);
}
/**
* Construct a new ViewingConditions instance. This constructor is for internal use.
*
* @param XYZ_w XYZ of adopted whitepoint
* @param L_A average luminance of visual surround
* @param Y_b adaptation luminance of color background
* @param sur the surrounding
* @param RGB_w the white point in RGB values (equations 7.4-6)
* @param RGB_c the adapted RGB values (equations 7.4-6)
*/
private ViewingConditions(
double[] XYZ_w, double L_A, double Y_b, Surrounding sur, double[] RGB_w, double[] RGB_c) {
this.XYZ_w = XYZ_w; // XYZ whitepoint
this.L_A = L_A; // average luminance of visual surround
this.Y_b = Y_b; // adaptation luminance of color background
this.surrounding = sur;
// calculate increase in brightness and colorfulness caused by brighter viewing environments
double L_Ax5 = 5.0 * L_A;
double k = 1.0 / (L_Ax5 + 1.0);
double kpow4 = Math.pow(k, 4.0);
F_L = 0.2 * kpow4 * (L_Ax5) + 0.1 * Math.pow(1.0 - kpow4, 2.0) * Math.pow(L_Ax5, 1.0 / 3.0);
// calculate response compression on J and C caused by background lightness.
n = Y_b / XYZ_w[1];
z = 1.48 + Math.sqrt(n);
N_bb = 0.725 * Math.pow(1.0 / n, 0.2);
N_cb =
N_bb; // chromatic contrast factors (calculate increase in J, Q, and C caused by dark
// backgrounds)
// calculate achromatic response to white
double[] RGB_wc = new double[] {RGB_c[0] * RGB_w[0], RGB_c[1] * RGB_w[1], RGB_c[2] * RGB_w[2]};
double[] RGBPrime_w = CS_CIECAM02.CAT02toHPE(RGB_wc);
double[] RGBPrime_aw = new double[3];
for (int channel = 0; channel < RGBPrime_w.length; channel++) {
if (RGBPrime_w[channel] >= 0) {
double n = Math.pow(F_L * RGBPrime_w[channel] / 100.0, 0.42);
RGBPrime_aw[channel] = 400.0 * n / (n + 27.13) + 0.1;
} else {
double n = Math.pow(-1.0 * F_L * RGBPrime_w[channel] / 100.0, 0.42);
RGBPrime_aw[channel] = -400.0 * n / (n + 27.13) + 0.1;
}
}
A_w = (2.0 * RGBPrime_aw[0] + RGBPrime_aw[1] + RGBPrime_aw[2] / 20.0 - 0.305) * N_bb;
D_RGB = RGB_c;
}
