RGB to (L,a*,b*) conversion using an ICC profile

Question

I want to use MATLAB to convert rgb to Lab using AdobeRGB.icc. I know how to convert using srgb.icc.

         cform = makecform('srgb2lab');
         lab = applycform(rgb, cform);

However, I don't know how to use AdobeRGB.icc to convert. First, we can read icc profile by:

         p = iccread('AdobeRGB.icc');

But I don't know how to continue. Any suggestions? Thanks!

Answer 1

Have a look at p - does it contain a field "MatTRC"? (I hope so!)

This is most likely a rgb2xyz transform. (Check p.Header.ConnectionSpace)

Actually, if you look with edit makecform and dig into the code a little, you will see that if you call makecform with an input such as 'srgb2lab' they just create two transforms, 'srgb2xyz' and 'xyz2lab', and then apply them in sequence. So we can do the same - using your icc profile for the rgb2xyz part, and the built-in for the xyz2lab part:

% 'forward' is rgb2xyz
cform1 = makecform('mattrc', p, 'Direction', 'forward');
cform2 = makecform('xyz2lab');
xyz = applycform(rgb, cform1);
lab = applycform(xyz, cform2);