[Openicc] Ghostscript PDF/X-3

[Kai-Uwe Behrmann]

Am 22.03.12, 21:36 -0700 schrieb Michael Vrhel:
> So you need to realize that Ghostscript will render to a number of
> different "Output Devices"   These devices can have different color models
> compared to the color space specified by the the OutputIntent.  For
> example, suppose I am rendering a source PDF file with a CMYK OutputIntent
> to a PNG "device".   This is a real situation that Ghostscript has to
> handle in a proper manner.  This process is going to generate a PNG file,
> which will have an RGB color space.   I would argue that for this
> situation, it makes sense for the OutputIntent profile to be used as a
> proofing profile since it describes the intended target of the source
> file.  It certainly can not be used as the final destination profile.   The
> user is free to specify what profile they want for the final data through
> the use of the -sOutputICCProfile= option.  For example they may want to
> use a Wide Gamut RGB space or simply sRGB.  If one is not specified,
> Ghostscript will by default use an sRGB profile.  This profile is put into
> the PNG file and the RGB color data which was mapped to the color space
> defined by that profile should provide a representation of what the
> intended output would appear if it had been displayed on a device described
> by the OutputIntent.   Acrobat Reader behaves in this manner if one was to
> open the source PDF file for viewing on the screen.

After a long IRC conversation with Michael Vrhel, I would like to 
inform you about the obtained clearifications for printing PDF/X-3 
documents regarding proper profiling and client side colour management.

As was said, -dUsePDFX3Profile=[#X] specifies a proofing profile.
For the linux printing chain, the print filter is responsible to select 
the desired OutputIntent. In case of a found OutputIntent, the print 
filter should omit especially the -sOutputICCProfile option. That way 
DeviceXXX/ will be assumed to be in the -dUsePDFX3Profile=[#X] alias 
OutputIntent's specified colour space and will not be further touched, if 
the OutputIntent, the DeviceXXX/ and the logical output colour space all
match.

To prevent above mentioned DeviceXXX/ mismatches, the profiling client has 
to check the print queues logical colour space, select a fitting target 
and attach the correct OutputIntent ICC profile with the same colour 
space. A conflict would happen if e.g. OutputIntent says rgb and colour 
numbers are defined as DeviceCMYK/.

kind regards
Kai-Uwe