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

Tomas Rokicki rokicki at gmail.com
Sat Jan 26 22:19:16 CET 2019

TexLive, which will include pdftex, is moving to github.


The file you are looking for is


Note that github is still not the "single truth" for TeXLive but it may be
getting there.


On Sat, Jan 26, 2019 at 1:12 PM Doug McKenna <doug at mathemaesthetics.com>

> Tom -
> Thanks for the info what happens with EPSF text files.  That makes sense.
> For PDF, I've now read up on the two pdftex primitives, \pdfximage and
> \pdfimageresolution in the pdftex manual, Section 7.5 of, e.g.,
> <http://vlado.fmf.uni-lj.si/texceh/kako/tex2pdf/ex/pdftex-s.pdf>
> \pdfimageresolution is a settable parameter relied upon by \pdfximage, and
> this parameter defaults to 72 (big points) if never set to something else
> (i.e., if it's 0).
> So I think that answers my question, which is that the TeX source code
> invoking the primitive \pdfximage is in charge of knowing and declaring any
> resolution other than 72/inch, and that the primitive \pdfximage doesn't
> care what the bounding box numbers are associated with the image file.  It
> appears that \pdfximage just scales them by \pdfimageresolution before
> doing other stuff to manage or record the image into the node tree, and its
> default is to treat the numbers it finds as measuring big points
> (PostScript points).  So setting \pdfimageresolution to 72.27 converts the
> sizes of a PDF image into the same exact size on the TeX page.
> All of this is presumption from reading the documentation.  I'm not sure
> where the source code (change file?) for \pdfximage can be perused to know
> for sure.
> Onward, into the fog ...
> - Doug McK.
> From: "Tom Rokicki" <rokicki at gmail.com>
> To: "Doug McKenna" <doug at mathemaesthetics.com>
> Cc: tex-k at tug.org
> Sent: Saturday, January 26, 2019 10:49:26 AM
> Subject: Re: [tex-k] Where does conversion of PostScript pts to TeX pts
> occur?
> The EPSF macros literally read the EPSF file line by line looking
> for the bounding box.
> The scaling by 72.27/72.00 is done when the bounding box numbers
> are interpreted in Don's bp dimensions directly in the EPSF macros.
> The EPSF macros are pretty simple; you can look at them directly.
> I don't know what happens for PDF.
> -tom

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