Hi again Hille,
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1118385
Towards the (current) end of that bug it seems suspicion is falling on
libpng. I guess I will cc the bug here.
The submitter told that the issue occurs only for some kind of pictures,
Sounds reasonable.
would like to have clarified in the first step if the characters which
differ are generated by code in the pdfTeX binary, or if we have to
blame one of the libraries pdfTeX is linked with.
I don't have the brain to be able to look at that hex dump and have any
real clue as to where it came from. It could be part of a png image with
those "unspecified" bytes as mentioned in the bug report (/FlateDecode
.. stream ...). Or maybe it's not. I don't know.
If it is due to libpng, though, I think I agree with Norbert's last
comment that it should be fixed in libpng, not in every program that
uses libpng. (I definitely won't be able to do anything about that.)
The testbed I have currently is 25 MB, i.e. far from being
minimal. I can provide it, but only on request.
Well, if you send it (or a url to it), I can at least see if the bug
reproduces for me. I see the OP in the bug report was using x86_64, so
it's probably not system-specific.
As a workaround for the reproducible doc: what occurs to me is that
perhaps doing a(n insignificant) transformation on the particular
image(s) will avoid the bug, wherever/whatever it is, and make the doc
reproducible. --best, karl.
