[Openicc] printer, driver, CUPS, PPD, printing GUI, ICC-profiles, colord, Oyranos, taxi....

[Kai-Uwe Behrmann]

Am 25.01.12, 12:16 -0800 schrieb Michael Sweet:
> We can choose to pass calibration data to Gutenprint, perhaps through ICC profile metadata, but that doesn't solve the general profiling case and requires a special app to profile just for Gutenprint.

It would be possible to standardise on a meta data tag for ICC profiles. 
However, how can a profiling application know that this tag is feeded to 
the rastertoprinter filter? Can a *toraster filter advertise inside the 
IPP protocoll that it is potential to do so? (I remember fuzzy *toraster 
was in CUPS a member of a one way chain.)

> We can also choose to support an uncalibrated 16-bit DeviceN space where 0 means no ink and 65535 means 100% ink (for each color). This supports having a general profiling application and is not driver-specific.  And certain key information (such as number and type of colorants) could be supplied as PPD keywords for the Gutenprint driver ("this is a 7-color printer with C, LC, M, LM, Y, K, LK inks") which would take care of the initial defaults when working with standard colorants for the printer.

I am afraid such 7/8-channel profiles will currently be very large. ICC 
has no mechanism to define C+LC->combinedC conversions in order to store a 
calibration in smaller tables. The profile must currently contain a table 
from all source channels to the destination channels and back for the 
inverse table. We get for a 8-channel by very poor 9 grid points
134,217,728 table points * 3 PCS channels. Thats for one table. Add to 
that a different perceptual and relative colorimetric flawour and we can
currently take that as a theoretical thing.

In the ICC are various ideas discussed to solve the size issue for 
n-channel ICC profiles. But none is actual implemented in a real 
world CMM.

However I find your idea very interessting. In case IPP defines some way 
to print uncalibrated n-channel, it will be used once ICC has overcome its 
n-channel issues.

kind regards
Kai-Uwe