[Openicc] Ghostscript PDF/X-3

[Michael Vrhel]

I'm a little confused. Possibly for different reasons.

>
> There are two kinds of PDF/X-3 (I'll include variants 4 and 5 as well),
> those with an OutputIntent embedded ICC profile, and those without - merely
> the output condition identifier is present (a printing condition not in the
> ICC registry).
>
> If the embedded profile is included, my expectation is that no flags are
> required for the OutputIntent to be used as the destination space. Any
> /ICCBased or Lab object, is converted to this destination using the
> embedded Output Intent profile. So does -dUsePDFX3Profile cause
> OutputIntent to be used? What if it's not present, what happens to this
> PDF/X-3 document?
>
> Chris,  At this time if -dUsePDFX3Profile is not specified, Ghostscript
will behave in its previous behavior of ignoring the OutputIntent.  This
was done primarily to minimize  significant changes (even if it is the
right change) in output for a default command line that customers and users
are currently using.  It may be that in the future Ghostscript will behave
by default with this option, but for now that is not the case.  Many of our
customers are software RIP vendors and they may very well end up using
Ghostscript with the -dUsePDFX3Profile option.


> An additional flag for proofing condition is appropriate, where the
> intermediate destination is the OutputIntent, and the final destination
> space is the proofing space (display or proofing system). And possibly a
> flag for rendering intent, as some may prefer RelCol, other may prefer
> AbsCol.
>
> -sOutputICCProfile= sounds to me like an OutputIntent override. I think
> everyone can predict in advance what I think of this, if it is what I think
> it is.
>
> Please feel free to refuse all of my premises and conclusions if that is
> easier.
>
>
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.



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