Pawel, this resolution entry is used if Ghostscript has to turn
graphical content of the PDF into a bitmap if PostScript does not
support this type of graphical content, especially transparency. A
bitmap always needs a resolution, also if the source data is entirely
vector graphics. If the resolution is not specified Ghostscript uses 720
dpi and Poppler (/usr/bin/pdftops) uses 300 dpi, which caused the slower
rendering of Ghostscript's output in a PostScript printer
(http://bugs.ghostscript.com/show_bug.cgi?id=693016). Also the mismatch
of the resolution raster, as 720 dpi on a printer with 300/600/1200 dpi,
can cause slow rendering of a bitmap in the printer.

To overcome these problems I have introduced to specify the resolution
and for that choosing the one fitting best to the job, usually taking
the setting of the "Resolution" option. Unfortunately, there are PPD
files without "Resolution" option or choice names do not tell about the
actually used resolution, some have marketing-designed choice names with
numbers much higher than the actually used resolution. If there is no
"Resolution" option I have used CUPS library functions to analyse the
PostScript code in the PPD to discover which resolution is actually
used.

Now I have changed the code to start with analysing the PostScript in
the PPD and falling back to the choice names of the "Resolution" option
if the PostScript does not deliver anything useful. This I will soon
make available as an update.

In any case, if there is no hint to the resolution used for printing a
job we fall back to 300 dpi, as this works with most PostScript (laser)
printers and output quality is not behind Poppler.


** Bug watch added: Ghostscript (AFPL) Bugzilla #693016
   http://bugs.ghostscript.com/show_bug.cgi?id=693016

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https://bugs.launchpad.net/bugs/984082

Title:
  Evince produces low-res, pixelated output when printing PDF's

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