PostScript - Error when Using Ghostscript "pdfwrite"

Question

I want to preface this with the understanding that I am working with legacy code and thus I am having to live with less than ideal situations and am doing some quirky stuff because of that. Until I can get approval to rewrite, I will have to make due.

Context

Here is my situation. The application is a "simple" one in that it reports off of a SQL database. For better or for worse it builds its reports with postscript. It make use of Ghostscript dlls in which it has embedded into the application directory. Here is the kicker, it has been requested that I include SSIS reports whose output is already in PDF format. For compatibility sake, i need to convert these PDFs into postscript even though in most situations they will be converted right back to PDF later on. I know this is most likely bad design but there is certain functionality that requires this and it just is what it is for the time being. I am using GhostScript to handle the conversions.

Observed Behavior The following behavior is what is observed once the PDF is converted to PS, passed through the application, and then converted back to PDF.

When using the "sDevice=pswrite" everything works except that the reports are compiled with poor resolution despite how I tweek the resolution option.

When leveraging "sDevice=ps2write" which I understand to be the current accepted protocol, the PDF will not render back and produces the following error.

ERROR:
undefined
OFFENDING COMMAND:
U1!‘WVt92\a
STACK:
--nostringval--
20

The above error is only produced when using a report from a report server that is accessed via web client. I can confirm that the PDF returns successfully and is not corrupt.

When running local SSIS packages on the application the produced PDF is able to be handled successfully.

When the origional PDF is converted to PS using PS2Write the comments are populated as follows

%!PS-Adobe-3.0
%%BoundingBox: 0 0 612 792
%%Creator: GPL Ghostscript 905 (ps2write)
%%LanguageLevel: 2
%%CreationDate: D:20171003154139-05'00'
%%Pages: 3
%%EndComments

pswrite produces

%!PS-Adobe-3.0
%%Pages: (atend)
%%BoundingBox: 21 30 761 576
%%HiResBoundingBox: 21.600000 30.400000 760.566016 575.100000
%.....................................
%%Creator: GPL Ghostscript 905 (pswrite)
%%CreationDate: 2017/10/03 15:53:40
%%DocumentData: Clean7Bit
%%LanguageLevel: 2
%%EndComments
%%BeginProlog

Suspicion

I am suspecting that either the PDF is in an incompatible standard that cannot be converted to PostScript. For example, a newer PDF version that cant be handled. Or perhaps it contains something that is incompatible such as a font or img.

Is there anyway to hunt this down for sure? Has anyone come across similar situations and what was the solution? Any pointers as to what to look into or things to try?

Answer 1

To be honest, nobody is likely going to be able to help without seeing the original PDF file. Even a dummy file will be fine provided it exhibits the error.

However, the first thing that springs to mind is that you appear to be using Ghostscript 9.05. That is now 5 years old, the current release is (about to be) 9.22. There have been numerous fixes to ps2write in that time, at least 50 or more, and the first thing I would suggest you do is upgrade and see if the problem goes away.

Secondly, you haven't been clear on why you need to convert the PDF files to PostScript. If all you are doing is feeding those back through Ghostscript along with some additional PostScript in order to convert the assemblage into PDF, you do not need to turn the PDF files into into PostScript first. Ghostscript is entirely capable of taking a mixture of PDF and PostScript files, so you can simply inject the PDF in between the PostScript from your SQL output to produce a single combined PDF.

This has a number of advantages; first and most obviously, you shouldn't get your conversion problem. Secondly, any construct in the PDF file which cannot be represented in PostScript (eg transparency) means that the content will be rendered to an image and the PostScript will simply contain a big bitmap. Just like the pswrite output, avoiding conversion means that won't happen. Thirdly it will be quicker than first converting all the PDF files to PostScript.

If you absolutely can't do that, then I would try current code and see if its better. If not then you have found a bug and I would suggest you report it at https://bugs.ghostscript.com you will need to be able to supply an example file and command line though.