Hello Marti, hello Leonard
It is necessary to make a difference between preserving an adjusting
pure grey and preserving and adjusting original separations.
For repurposing CMYK-data, it is absolutly necessary to have the
functionaly to preserve and adjust pure grey.
A functionality of also preserving the original separations is "nice to
have for high-end users"
So it makes definitly sense to integrate a functionaly for preservinig
AND adjusting pure grey in lcms in the next version
Functions for preserving original separations can be tested implemented
later.
All applications which are may be used for CMYK2CMYK with lcms would get
better results e.g.
- PDF Enhancer 3
- Imagemagick
- Scribus
....
:-) Jan-Peter
Marti schrieb:
Hi Jan-Peter,
As lcms actually the described functionality for mapping pure grey /
building such devicelinks on the fly ?
That's what I'm trying to do. The tone map already works. That is, pure
K of origin is converted to pure K of destination in a way L* is
preserved. No CMY is involved here. Then comes the difficult part,
recompute the amounts of CMY to obtain same color. And here it would be
nice to preserve the separation whatever possible. But this is, right
now, not my primary goal.
Unfortunately, this is *very* complex, mostly because many profiles have
AToB/BtoA tags of different resolution/accuracy, so AtoB is not the inverse
of BToA in many cases. Therefore, a robust algorithm should compensate
those differences in order to get consistent results. Pfew!
Regarding TAC... There is actually a cmsCreateInkLimitingDeviceLink()
function that allows you to apply TAC. But that is pretty limited as it
uses the hypercube algorithm. For a more advanced inklimit, we would
need some additional information (i.e., ink weight curves) which is not
available on the profile.
Regards,
Marti.
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Jan-Peter Homann ------------- mobile +49 171 54 70 358
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