[cups-devel] When to use -dNOMEDIAATTRS when calling Ghostscript

[Helge Blischke]

> Am 16.08.2016 um 00:16 schrieb Till Kamppeter <till.kamppeter at gmail.com>:
> 
> On 08/15/2016 06:20 PM, Michael Sweet wrote:
>> Till,
>> 
>> NOMEDIAATTRS is intended to disable the default Adobe media matching algorithm, ...
> 
> Another question: Is there any problem using -dNOMEDIAATTRS when Ghostscript's input is PDF?
> 
>   Till
> 

No, there should be no problem, as PDF input is handled by Ghostscript using its PostScript interpreter
with a couple of additional operators. Especially the pdfpage operator internally calls the standard
setpagedevice operator which in turn evaluates the NOMEDIAATTRS option.

To make clear what this option really means (from the Ghostscript sources, especially from the initialization
PostScript routines):
-dNOMEDIAATTRS 
sets the default media selection policy to 7 and thus reduces the set of page device keys which influence
the media selection according to the Adobe conventions (see the PLRM 3rd ed.) to only the
/PageSize key, ignoring all others.

The idea behind this is that the media selection algorithm is highly vendor- and printer-specific and cannot be
reliably implemented by non-printer dependent software. These dependencies usually are described
(as far as syntactically possible) by the UI constraints statements in the respective printer’s PPD, and thus
subject to e.g. the pstops or pdftops filter.

Helge