[Lcms-user] Apply profile with PCS = cmsSigXYZData, Color Space = cmsSigGrayData

[Aaron B. <bo...@gm...>]

Hello,

I have a jpeg 2000 file with an ICC profile.

PCS is cmsSigXYZData and color space is cmsSigGrayData.

The file can be found here:
https://github.com/GrokImageCompression/grok/issues/38

I am working on a library that decodes the jpeg 2000 file and applies the
ICC profile, using LCMS.

Currently, I have this code:

 in_type = TYPE_GRAY_8;
 out_type = TYPE_RGB_8;
 out_prof = cmsCreate_sRGBProfile();

and I can create the transform and apply the ICC profile, but the output is
an RGB file.
What I would like is to output a grayscale file.

So, if I instead call

out_prof = cmsCreateGrayProfile(NULL,NULL);

then cmsCreateTransform  returns NULL and I can't apply the profile.


What is the best way of creating a transform for this kind of grayscale
image ?

Thanks so much,
Aaron