[scribus] Need help please for PDF export re transparency

[ZASKE Martin]

Dear list,

our book is getting ever more ready to be sent to the printers. They
told me they would prefer PDF/X-4 but they can also handle PDF/X-3 and
some other formats.

I am using Scribus scribus-1.5.3.svn-snapshot-170430-x64.exe on Windows
10 pro because 1.5.3 is handling our local language much better than any
previous Scribus-version (we have tone-marks on top of special vowels,
which used to float away from their host-vowel).


Our book will have one colour-file for the cover, printed on the outside
only. No problem so far.

And then some 200+ A5 inside-pages in black/white only. A text-frame on
each page. A master page with the page-number at the bottom. And most
pages carry one or two nice black/white line drawings from a
professional illustrator from Sweden. We are using three layers for
text/illustrations/captions.

Those illustrations were sent to us as .tif files, as far as I can tell
no alpha-channels involved. I can edit these files maybe but I cannot
order different ones.


The layout is almost complete for the inside-pages. But when I try
opening the PDF-export in Adobe Acrobat Reader (2017 release, version
2017.009.20044), I get the error message "There was an error processing
a page. Invalid Transparency Group".

When I open the PDF in the Windows app called "Reader" I get no error
message and all pages open properly and are looking correct, including
the illustrations.

Next I tried exporting to PDF 1.5 instead of PDF/X-4 and I am getting
the same error message from Acrobat Reader: "There was an error
processing a page. Invalid Transparency Group".

I have googlet this error message and have had a single hit in Russian
from 2008. I found many pages explaining general stuff about
transparency and PDF.


So where in my export-file do I have problematic transparency?

If we had Adobe Acrobat, I could use "List transparent objects" in the
Preflight tool. But our project is mainly open-source (not least for
budget reasons but also so that other local projects in African can use
our templates and our methods).

Does any user know how to check our files for "forbidden transparency"
with an open-source tool? Or can you give me hints what/where in my
Scribus document is creating those bad transparencies.

For legal reasons, I cannot send the entire file, but I could send a
sample-export of a few pages; I tried with the first 8 pages only and
got the same error.


Background: We have published with previous Scribus versions for years.
We always used PDF-exports for printing; both on our own laser-printers
and also commercially in Africa on plastic-sheets in digital printouts
and in Germany for professional digital printing on paper. So far we
never had any error messages and we never had "broken" PDF files; all
prints always looked fine.

Could this be a side-effect of using 1.5.3?

Any help is welcome, time flies..., thanks,

Martin





-- 
ZASKE Martin
responsable GʊGʊ
BP 50 - Bassila - Bénin
tel GʊGʊ 66.66.11.11
tel pers 97.44.62.95