Thanks - I tried using a copy of
https://github.com/Enyby compiled on my Mac, though it works for several pbt files, but on yours it seg faults after writing a few black images...
The pbres binary in the SDK doesn't seem to have an option to extract all the resources at once. You can extract one at a time
but they're still in their internal "res" format (well,
file(1) says "PDP-11 separate I&D executable" but that seems unlikely) and not BMP.
The SDK pbres has an "unpack_resource" function which (decompiled) seems to uncompress the data and write that as an unchanged blob to disk; Enyby's code for "pbres -u" does the same (and gives identical output) but Enyby's "pbres -d" code tries to convert it to a BMP.
So I wonder if the internal res format has changed?
Your file is still a v1 theme BTW.