Page 86 - Computational Colour Science Using MATLAB

IMPLEMENTATIONS AND EXAMPLES 73

dc^2);

% get the polarity of the dh term
dh = dh*dhpolarity(lab1,lab2);

% now compute the CMC weights
if (lab1(1)<16)
Lweight = 0.511;
else
Lweight = (0.040975*lab1(1))/(1 + 0.01765*lab1(1));
end
[c,h] = car2pol([lab1(2) lab1(3)]);
% require C*ab and H*ab of standard
Cweight = 0.638 + (0.0638*c)/(1 + 0.0131*c);
if (164 < h& h < 345)
k1 = 0.56; k2 = 0.20; k3 = 168;
else
k1 = 0.36; k2 = 0.40; k3 = 35;
end
T = k1 + abs(k2*cos((h + k3)*pi/180));

F = sqrt((c^4)/(c^4 + 1900));
Hweight = Cweight*(T*F + 1 - F);

dl = dl/(Lweight*paral);
dc = dc/(Cweight*parac);
dh = dh/Hweight;

de = sqrt(dl^2 + dc^2 + dh^2);

The function cie94de computes the CIE94 equation and operates in a similar
manner to cielabde and cmcde with the following format:

[de, dl, dc, dh] = cie94de(lab1, lab2)

Box 13: cie94de.m

function [de,dl,dc,dh] = cie94de(lab1,lab2)

% function [de,dl,dc,dh] = cie94de(lab1,lab2)