[NTG-context] LuaTeX and PDF.js

Hans Hagen j.hagen at xs4all.nl
Thu Jan 7 23:01:57 CET 2021

On 1/7/2021 10:10 PM, Vedran Miletić wrote:
> Hello,
> I compared latest ConTeXt standalone (LuaTeX 2.08) against TeX Live 2020 
> (LuaTeX 1.12). The produced PDFs are:
> https://miletic.net/lipsum-112.pdf
> https://miletic.net/lipsum-208.pdf
> Viewing them with Evince (and I assume Adobe Reader, I don't have it at 
> hand to test) shows only minor differences in (horizontal) character 
> spacing, which I would expect; the text looks reasonably good either 
> way. However, viewing them with PDF.js shows a large difference:
> https://miletic.net/lipsum-pdfjs-112.png
> https://miletic.net/lipsum-pdfjs-208.png
> As you can observe, b, m, n, p, and r (and possibly others) are moved 
> slightly above other letters. Is this the expected behavior? If not, is 
> this an issue with the way PDF.js is displaying the PDF or the way 
> LuaTeX is producing it?
what lua does your 2.08 have? if it's 5.2. then such small differences 
can be a side effect of lua (different number models), serialization of 
numbers (default accuracy), or maybe rounding in the lua=>tex font 
interface (there were some fixes iir), the number of digist that the 
backend uses, etc

anyhow, so what you see (in the file) is (per line) transform matrices 
that are slightly different so what you then see is rounding to the 
device pixels

i wouldn't loose sleep over it .. nowadays fonts also evolve and that 
gives larger differences


                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl

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