[tex-k] Where does conversion of PostScript pts to TeX pts occur?

[Karl Berry]

Hi Doug,

    Or does the implementation (in WEB, or C, or whatever) of some primitive
    command parse the graphic data to get the bounding box?

I thought it might be worth mentioning that although pdftex.web has the
conversion of dimensions, the actual parsing of pdf files being included
is done by separate libraries, different for each engine in the current TL:

pdftex - libs/libxpdf/ which we constructed for TL years ago from xpdf code.
(Distros typically replace this with poppler.)

xetex - libs/poppler/ which also started from xpdf long ago, but by
other (non-TeX) people who have continued to develop and release it as a
separate library. It's used extensively

luatex - texk/web2c/luatexdir/luapplib which was originally written by
Pavel Jackowski long ago and was recently revived by Luigi Scarso et
al. for LuaTeX, which before now also used poppler.

If you feel like turning your eagle eye on pplib at some point, that
would be great. Our hope is that for 2020 we'll able to use it for all
three engines. The advantages for us are that it is written in C, not
C++, and that it is maintained within the TeX world, so we don't have to
worry about extensive prerequisites getting imposed by third-party
maintainers who could care less about TeX.

Also, libxpdf and especially poppler have tons of features we don't need
or want, which just complicate things.

Hope this bit of background helps. -k