[Openicc] Alternative CUPS Raster based print color workflow

[Jan-Peter Homann]

Hello Krita team and Open ICC list,
in the discussion of the last two weeks, we learned, that the libreries 
for generating PDF spool files are fare away from handling other PDF 
colorspaces than DeviceRGB.

For CUPS itself, it is not mandatory, that the print spool file must be 
PDF (or legacy PostScript..). At www.cups.org it is stated, that also 
completly raster based print workflows are possible.

For implementing color management in the CUPS environment, this would 
allows follow scenario

1) sRGB canned profile approach for PDF (and legacy PostScript) print 
workflows
This is a workflow we already have talked here on the list, and which 
probably will be implemented with GhostScript as the XXXtoraster engine 
in the future

2) ICC based print raster workflow
This would be an alternative CUPS workflow with only a rastertoraster 
filter. This workflow is dedicated to all ICC aware LINUX imaging apps, 
which are able to export a raster file with the document colorspace as 
an embedded ICC-profile.

The rastertoraster filter is mainly littleCMS with some wrapping around to
- read the embedded profile of raster spool file as source profile in 
littleCMS
- to use the cupsIC profile workflow to be configured as target profile 
in littleCMS

 From the standpoint of the driver vendor (e.g. Gutenprint, Turboprint 
or other...), they concentrate on settings with ICC profiles and the 
support of cupsICCprofile.
Handling the different kind of spool files is part of CUPS configuration.

If such a additional CUPS configuration has a clear naming e.g. 
"ImagesOnly-Printer" and must be manually installed by the user, we have 
follwoing scenario:

1) The standard CUPS installation in the distro is PDF / PostScript sRGB 
only
2) Users which are interested in advanced color workflows, can download 
the alternatice "ImagesOnly-Printer" installation
3) Both installations can make use of the same cupsICCprofiles driver setups
4) App vendors like e.g. Krita have only to provide an image with 
embedded document profile as print spool file to a standardized CUPS 
interface.

Krita team:
Could you imagine to support this sketch of a workflow ?


Kind regards
Jan-Peter



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