Commit 8d69148 broke PDF/A-1b output by adding transparency

[ppietikainen]

Hi,

I have a PDF/A-1b thesis template, using pdflatex, \usepackage[a-1b]{pdfx}, .xmpdata and all that. Very fragile, but passes the current requirements. Hopefully they'll demand UA-2 soon, which I am 99% ready for with lualatex.

Suddently my GH Actions VeraPDF CI/CD started failing due to transparency. As a workaround I can (thanks Gemini!)

\usepackage[a-1b,latxmp, mathxmp]{pdfx}[2017/05/18]
\def\Gread@pdf#1{%
\let\Gin@decode@empty
\Gin@interpolatefalse
% \Gread@transgrouptrue % <--- WE REMOVE THIS LINE
\Gread@pdftex{#1}%
}

but maybe the code could be a bit smarter and not try to force transparency if someone is using legacy packages like I am...

[davidcarlisle]

I note that you already raised this as

latex3/latex3@4c017aa#commitcomment-174677846

why do you have a requirement for A-1b which seems rather weird?

Rather than make everywhere test for PDF/A requirements it would probably make more sense to make \Gread@transgrouptrue and related commands defined to do nothing at the point that you specify A1-b, in which case it would not be a change in this repo.

[u-fischer]

I don't that you can do it with a simple redefinition, as that is a simple boolean, and it must be set to false if the transgroup should not be used. We could test for the pdfversion and suppress the code if it is 1.4 or smaller, but that would require that the document properly set the version (pdfx doesn't do it). Or offer some option to disable the code.

Personally I would simply use A-2b instead.

[ppietikainen]

Yea, that was my first guess for this regression but that led nowhere for a workaround.

PDF/A-1b is what gets enforced on us by the university (Due to being "Archival ready"). Word to PDF to A-1b converter (that randomly removes e.g. fi-ligatures from LaTeX-generated PDF's) is the usual chain. They will probably only support/require UA-2 when the average humanities student / automated tool can generate those easily from Word. UA2 would actually even be pretty close to a legal requirement, except it's considered to be the student "publishing" so it's considered not to be.

I guess this kind of check could be added to pdfx too? At LaTeX level PDF < 1.4 is easy (no transparency), PDF 1.4 does support it (but with A-1b not allowed), so it does get hairy.

Currently it's only my CI/CD pipeline, but if this ever hits Overleaf I'll actually have to even implement the workaround (unless e.g. pdfx gets updated at the same time, if the check goes there). Or I'll just harass the people doing the people doing the thesis upload system to accept UA-2 documents, which I and my students can generate just fine...

[josephwright]

I don't that you can do it with a simple redefinition, as that is a simple boolean, and it must be set to false if the transgroup should not be used. We could test for the pdfversion and suppress the code if it is 1.4 or smaller, but that would require that the document properly set the version (pdfx doesn't do it). Or offer some option to disable the code.

I think for the case in hand

\let\Gread@transgrouptrue\Gread@transgroupfalse

would do it.

[u-fischer]

Well you do not have to discuss about UA-2 and such modern stuff.

A-1b is not recommended with UA-1 and so basically doesn't support and any accessibility setting. See the best practice https://pdfa.org/resource/conforming-to-both-pdf-a-and-pdf-ua-best-practice-guide/

[FrankMittelbach]

Or I'll just harass the people doing the people doing the thesis upload system to accept UA-2 documents, which I and my students can generate just fine...

you should really do that. For anybody cares for real accessibility rather than a checkmark by some checkers UA-2 it is basically the only way to achieve that (unless the documents are truly trivial). Otherwise it is just a fig leaf upon unusable content, unusable for anybody who actually needs accessibility. 100% so if math is involved.

So please do the arrassing, it is needed on all fronts if we want to make the world a better place in this respect.

[ppietikainen]

Minimal \let\Gread@transgrouptrue\Gread@transgroupfalse did the trick .

I guess this could be pushed to pdfx upstream in the (if option a-1b do this path), but at least I'll conserve my energy and just concentrate on getting theses with image alt tags (and as much as possible other stuff) out there. With my current approach they are a no-go, but I do have a version that validates UA-2 and that does them just fine.

Thanks!