[cups] Printing quality differences when printing pdf using CUPS and app on MacOS

[Helge Blischke]

> Am 09.04.2020 um 19:24 schrieb Gregory Morse <gmorse at morseinc.com>:
> 
> Greetings. I have a strange situation I'm trying to find if anybody can
> help with.
> 
> I am printing the same PDF file on MacOS Catalina in two different ways: 1)
> Using CUPS on the command line and 2) using an app on the mac, i.e. Adobe
> Acrobat Pro or Adobe InDesign. Both are generally working well, but there
> is a small, but important issue. When I print the files using CUPS the
> print quality is slightly degraded compared to the output from CUPS, it's
> subtle, but different. What I've noticed is that the output from CUPS is
> the same as the output when printing from the Apple Preview App. So for
> some reason Apple Preview and CUPS print the file differently than Adobe
> InDesign and Acrobat. It's so strange, a PDF is a PDF right? Any
> suggestions?
> 

Well, printing an existing PDF from the preview app or by command line commands (lp command)
both initiate the same sequence of CUPS filters that convert the source PDF to
the data format the printer requires. the first step in this case is executing
one of the cgpdftosomething filters (where something is one of ps (postscript), pdf, or raster).

When printing from Acrobat (reader or professional) or InDesign, the first step is done
by the Adobe program itself, namely generating a PostScript job which is then transformed
by a CUPS filter pstosomething.

So it is plausible that both transformation sequences lead to (slightly?) different results.
To dig into the details, I’d propose you send me a sample PDF, I then could perform a
detailed analysis of what happens, especially with respect to color handling.

Helge