Bug#1118385: texlive-binaries: corner-case PDF image nondeterminism

Hilmar Preusse <[email protected]> writes:

> Control: forwarded -1 https://tug.org/pipermail/tex-k/2026-May/004330.html

Thanks!

As I recall, my pre-filing investigation found that libpng leaves any
trailing portion of the row's final byte unspecified.  It would of
course be possible to tighten that policy up, but there's normally no
need to, even from a reproducibility perspective, because such bits are
typically of no interest to consumers anyway.  As such, it falls on
pdfTeX and anything else that takes a similar approach to clear those
bits or otherwise populate them consistently.  In principal, doing so
after reading each row is safest, but observed behavior suggests that
clearing them up front should suffice.