[Openicc] Wrong color output of Xerox printer - Color Management problem?

[Jan-Peter Homann]

Hello all,
Under Mac OSX, the interactions of application based color management, 
OS-Colormanagement, CUPS and driver based colormanagement are 
intransparent, bad documented and very hard to troubleshoot.

I know several color professionals, which are avoiding Mac OS X and CUPS 
color management by generating PDF-files direkt from the application  
(if the application can do this on its own...) and put this PDF into a 
hotfolder of an external RIP.

Some hints to trouble shoot the problem:

Application and document
- Which application has been used for printing
- which kind of document has been printed
- does the document may contains placed content e.g. images with 
mebedded ICC-profiles ?

Changes in CUPS and GhotsScript:
- Can any on please decribe, what has changed in CUPS and GhostScript 
concerning color management ?
- do we have any pre setted color transformations in the new setup ?
(e.g. sRGB-data is converted to SWOP, if a CMYK printer is used...)
- do we have any ICC profile tagging on PDF object level
(this is something, which happens under Mac OS X, if the applications 
delivers DeviceRGB PDF objcets to the Mac OSX / CUPS print chain...)
- does the setup adds an PDF output intent to the print chain ?
- If yes, which output intent is used ?
- if yes, does GhostScript uses this output Intent for a color 
transformation ?
- What kind of data is delivered from GhostScript to to the driver:
     - RGB bimap data whith the same RGB values as delivered from the 
application without embedded ICC-profile
     - RGB bimap data whith the same RGB values as delivered from the 
application with embedded ICC-profile
     - CMYK bimap data without embedded ICC-profile
     - CMYK bimap data with embedded ICC-profile



To troubleshoot this and comprable problems I would recommend to create:
- a set of open documents like e.g.
     - JPEG, TIFF images in RGB and CMYK with and without embedded profiles
     - PDF-files
     - HTML-document with placed RGB images without embedded profiles 
and with embedded sRGB-profile
     - ODF document with placed RGB images without embedded profiles and 
with embedded sRGB-profile
     - A CMYK document with placed CMYK-image from e.g. Krita

We than need a solution to analyze and compare
- which kind of PDF has been created from the test document which is 
delivered through CUPS to GhostScript
- Which kind of bitmap file is created from this PDF-file by GhostScript 
and delivered to the printer driver


Best regards
Jan-Peter









Am 20.11.12 11:37, schrieb Till Kamppeter:
> Hi,
>
> after a certain update of Ubuntu some color printers from Xerox do not 
> print colors correctly any more, see
>
> https://bugs.launchpad.net/bugs/984424
>
> What changed during the development of Ubuntu is the color-managed 
> rendering by Ghostscript and also the color management support in the 
> surrounding CUPS filters.
>
> This can have negative effects on some color printers, due to their 
> own way to do color management, requirement of printer-specific ICC 
> when sending color-managed job, ...
>
> Can someone have a look and comment on the bug report? Please also 
> feel free to ask the reporters of the bug for additional information, 
> sample files, ...
>
> Thanks in advance.
>
>    Till
> _______________________________________________
> openicc mailing list
> openicc at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/openicc
>


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