[argyllcms] Re: Ink-limiting an existing profile

Oliver Schulz wrote:
>> With Argyll, I would do something like
>>
>>     icclink -v -qh -G -cpp -dpp -kt -l310 \
>>         EuroscaleCoated.icc EuroscaleCoated.icc limit.icc
> [...]
>> generation for the new profile as in the original one (note, when
>> creating a device link, -kt can be used, which which inherits the K
>> level from the source profile as far as possible, but when creating an
>> output profile from measurements, this is not an option).
>> On the other hand, applying the above mentioned device link to the CMYK
>> data after applying the original EuroscaleCoated profile will almost
>> preserve the original personality of the Euroscale profile, and change
>> it only as much as necessary to enforce the ink limiting.
>
> Thanks a lot for all your information Gerhard!
> This is exactly what i wanted - colorimetrically correct ink-limiting
> while preserving black-generation as much as feasible.
> (Well, in some cases reprofiling from measurements may be useful, of
> course, to optimize the new profile for the input gamut.)

But you shouldn't overestimate the difference. Though the LCMS method
will eventually result in gamut clipping, while the perceptual device
link I proposed above will do a smooth gamut compression, I nevertheless
guess that you won't see much difference for most images, particularly
if the ink limit isn't redcuced too much (and 350 -> 310 isn't IMO so much).

>> But I also don't know a ready to use Argyll or lcms tool which can
>> incorporate such a device link directly into the B2A tables of an
>> existing profile (but it should indeed possible and not too complicated
>> to develop one).
>
> Hm, that anticipates my next question. So, no luck, it seems. :-)
> Such a tool might make a nice addition to Argyll one day. ;-)

If you can live with a crude non-standard profile which works only with
perceptual intent in PCS -> device direction (i.e. a profile which
contains only a B2A0 table, but no B2A[12] tables, and no A2B tables)
then you can try

    icclink -o EuroscaleCoated-limited.icc -x -c2 -t0 "*Lab"
EuroscaleCoated.icc limit.icc

(notice, that here "icclink" is the LCMS icclink utility program, not
the Argyll one!)

Regards,
Gerhard



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