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

Doug McKenna doug at mathemaesthetics.com
Sat Jan 26 18:45:44 CET 2019

Thanks, Tom. 

But now I'm confused, because you're talking about an "epsf" *macro*, which sounds like something written in TeX that by virtue of being a macro must be relying on some even lower primitive command (a PDF extension command in pdftex?) to get the bounding box numbers from the graphics file living in the outside world. 

Does any TeX code, running on the TeX engine, actually parse the PDF (or EPSF) data to determine its bounding box? 

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

I'm trying to determine on which side of the TeX virtual machine/engine barrier the bounding box info in a PDF file gets converted to a fixed-point Dimension value stored inside the TeX engine. 

In other words, who is responsible for scaling the big point numbers by 72.27/72.0 to bring them into TeX's internal world, where all dimensions are stored as [16:16] fixed point numbers and where the integer part always measures points at 72.27/inch? 

- Doug McKenna 

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 9:47:58 AM 
Subject: Re: [tex-k] Where does conversion of PostScript pts to TeX pts occur? 

I'm sorry; I mean bp (big point) units. 

On Sat, Jan 26, 2019 at 8:46 AM Tomas Rokicki < rokicki at gmail.com > wrote: 

The epsf macro reads the bounding box and interprets it using 
TeX truept units. 

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