Kai-Uwe:
> The profiles contain stepped curves, everything else than smooth. So
> you seems to target at some posterisation effect.
That's right, that's precisely the goal of these profiles: obtain CMYK
that contain only certain levels of ink, no matter what is the original
RGB image. But, as I replied to Guy, in our current printing
architecture I can't use device links, I need to use output profiles,
that's why I am stretching the functionality of lcms.
> I have used such an approach, but not it in a normal transform. Only a
> device link can do that. lcms builds internally a device link, which
> will change your curves. With a device link your profile will be used.
Who said only device-links can do that? These profiles are doing it...
although with problems,
I'm afraid, though, that you are right: individual steps would deliver
the desired results, while combining all the curves and LUTs in a single
LUT that represents the final transform, as littlecms does (and most
CMMs), is preventing me to achieve my goal.
> The tables a all set to full or zero. I think this is intentional to
> hide them. Otherwise that would not work at all.
The CLUT forces the nodes to full or none, that's correct. But the CMM
will always apply interpolation to values between nodes. Depending on
the neighbouring nodes, the final CMYK values are unpredictable, and
that's the reason to include prelinearization curves: to clamp the lab
values to the nodes, with known final values.
As Marti suggested, I have also run into what seems like encoding problems.
> Possibly you can change the signature from output profile to device
> link and move the B2A0 to a A2B0 table with the according changes in
> the profile.
Nope, not an option, needs to be an output profile.
Building device links will come later... but I'm waiting for lcms 2.0 to
do that, since it incorporates Gamut Boundaries and plugins that will
ease that development.
Thanks a lot, Kai-Uwe,
Ignacio
--
______________________________________________________________
Ignacio Ruiz de Conejo
Senior Imaging Researcher
Tel. : +61 28875 9682
e-mail: ignacio.ruizdecon...@silverbrookresearch.com
______________________________________________________________
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