Add a CMYK profile with a B2A0 profile.

[jrmuizel]

This would be nice for going from RGB -> CMYK

[saucecontrol]

I'm curious about your use case for this.

CMYK is a device-dependent color representation, meaning it is dependent on the ink, paper, and print equipment to be used. It makes some sense to say "I have a CMYK image that was incorrectly saved without a matching profile, and I want to show some approximation of it on the screen", which is why I have provided a single A2B0 profile. It's not meant to be correct, but it's good enough to get you a result so you can show something.

CMYK is really only useful for printing, so conversion should always use a profile that matches the device to be used. I can't think of a case where you'd want CMYK without the colors being correct.

[jrmuizel]

I wanted something small that I could check into the qcms repo for testing. So it only needs to small and somewhat plausible.

[saucecontrol]

Ah, gotcha. I only wrote the interpolation and fitting code for 4->3 channels, but I'll give it a look when I have time and see what it would take to fill in the other direction.