Page 121 - Computational Colour Science Using MATLAB

108 CHROMATIC-ADAPTATION TRANSFORMS AND COLOUR APPEARANCE

% step 9
A = (2*rgbpa(1) + rgbpa(2) + rgbpa(3)/20 - 2.05)*nbb;
Aw = (2*rgbpwa(1) + rgbpwa(2) + rgbpwa(3)/20 - 2.05)*nbb;

% step 10
z = 1 + sqrt(fll*n);
j = 100*(A/Aw)^(c*z);

% step 11
q = (1.24/c)*((j/100)^0.67)*((Aw + 3)^0.9);

% step 12
s = (5000*sqrt(a^2+b^2)*e*10*nc*nbb/13)/(rgbpa(1) + . . .
rgbpa(2) + 21*rgbpa(3)/20);

% step 13
c = 2.44*s^0.69*(j/100.)^(0.67*n)*(1.64-0.29^n);

% step
14 m = c*fl^0.15;

An example of the function is provided by the following code segment:

clear

% test sample
x = 0.3618; y = 0.4483; Y = 23.93;
xyz(1) = x*Y/y; xyz(2) = Y; xyz(3) = (1-x-y)*Y/y;

% white in test light
x = 0.4476; y = 0.4074; Y = 90.00;
xyzw(1) = x*Y/y; xyzw(2) = Y; xyzw(3) = (1-x-y)*Y/y;

xyz = xyz’;

xyzw = xyzw’;

yb = 18.0;
la = 200;
lw = la*100/yb;