Bug#847462: the problem is with CUPS
2017-03-04 20:43 GMT+02:00 Brian Potkin <claremont102@gmail.com>:
> On Fri 03 Mar 2017 at 20:28:56 +0200, Martin-Éric Racine wrote:
>
>> 2017-03-03 18:25 GMT+02:00 Francesco Potortì <Potorti@isti.cnr.it>:
>>
>> > This apparently has to do with the old problem of cups-pdf converting
>> > PDF to PS and back to PDF.
>> >
>> > I have an old Ubuntu Lucid installation where the problem does not
>> > exist.
>>
>> Debian and Ubuntu both briefly used a patch (around version 2.5.1
>> IIRC) that bypassed the pdf2pdf filter. It worked well for simply
>> passing documents that were already in PDF format over to CUPS for
>> output to a PDF spool. However, it completely broke CUPS-PDF's
>> primary functionality which is to convert arbitrary document formats
>> into PDF, and it also prevented users from further manipulating the
>> documents via CUPS-PDF's configuration file options before outputting
>> them to the PDF spool. This resulted in complaints from users who
>> depended upon these features, so I removed the patch.
>
> The fullest discussion of this I know of is at
>
> https://bugs.launchpad.net/ubuntu/+source/cups-pdf/+bug/820820
>
> Users should take note of the comment:
>
> > The reasons for not skipping this step are known to you
> > (it will severly impede the functionality of CUPS-PDF).
> > Furthermore, once again, CUPS-PDF is not meant for
> > processing PDF-input (i.e., it is not meant to be a
> > PDF-manipulation tool).
>
> However, cups-pdf is still seen as a general "convert something to a
> PDF" utility. At one time it might have served that purpose, but not
> now. Both text and PDF input produce a below-standard, non-searchable
> output. There is a case for clarifying its purpose as a cups-filters
> plus backend method for getting a decent quality, searchable PDF from
> PostScript input only. (Okular produces PostScript; Evince doesn't).
As far as I can tell, the reason why the quality of the output has
varied over time is because the quality of Ghostscript itself has
varied a lot.
There might be better filters than Ghostscript we could call to handle
the generic document conversion step. However, that's entirely
upstream's decision.
Martin-Éric
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