Re: Support alt text in LaTeX output

On Wed, 5 Aug 2026 at 08:50, Patrice Dumas <[email protected]> wrote:

> On Sat, Jul 25, 2026 at 08:46:56PM +0100, David Carlisle wrote:
> > the pdftitle and  alt text in includegraphics in the end have to be a PDF
> > encoded string with no markup, so
> > over the years latex has got better at "cleaning up text" basically now
> any
> > unicode text should work, the only characters that you need to quote are
> %
> > { }
>
> Seems like _ needs to be quoted too.  Maybe general text protection
> needs to be done, so also protecting $#, or even ~.
>

_ does not need to be quoted as you are making a string not typesetting

\DocumentMetadata{tagging=on}
\documentclass{article}

\usepackage{graphicx}

\begin{document}

\includegraphics[alt={some_underscore_text worth 50$}]{example-image}

\end{document}



runs without error giving the expected alt text on the figure

     <Figure xmlns="http://iso.org/pdf2/ssn"
        id="ID.08"
        alt="some_underscore_text worth 50$"
        xmlns:Layout="http://iso.org/pdf/ssn/Layout"
        Layout:BBox="{ 148.71233, 427.19861, 468.71155, 667.19801 }"
       >

 although if the string may be used in multiple contexts so might be
typeset as well as being used as a pdf string
and you want to be safe it's OK to quote them

\includegraphics[alt={some\_underscore\_text worth 50\$}]{example-image}

produces the same output here.



> --
> Pat
>