Page 89 - Computational Colour Science Using MATLAB

76 COMPUTING COLOUR DIFFERENCE

% function [de,dl,dc,dh] = cie00de(lab1,lab2,paral,
% parac,parah)
% computes colour difference from CIELAB values
% using the CIEDE2000 formula
% lab1 and lab2 must be 3 by 1 or 1 by 3 matrices
% and contain L*, a* and b* values
% The dl, dc and dh components are CIEDE2000 deltas
% The defaults for paral, parac and parah are 1
% see also cielabde, cmcde, and cie94de

dim = size(lab1);
if (dim(1) == 1) | (dim(2) == 1)
lab1 = lab1(:)’; % force to be a row matrix
else
disp(’lab1 must be a row matrix’);
return;
end
if (dim(2) *=3)
disp(’lab1 must be 3 by 1 or 1 by 3’);
return;
end

dim = size(lab2);
if (dim(1) == 1) | (dim(2) == 1)
lab2 = lab2(:)’; % force to be a row matrix
else
disp(’lab2 must be a row matrix’);
return;
end

if (dim(2) *=3)
disp(’lab2 must be 3 by 1 or 1 by 3’);
return;
end

if (nargin<5)
disp(’using default values of parametric values’)
paral=1; parac=1; parah = 1;
end

% convert the cartesian a*b* to polar chroma and hue