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August 23, 2005

PDF Accessibility

We physicists use a lot of PDF.

It’s the primary means of distribution of papers at the arXivs. It’s what we use to distribute class notes to students. The NSF requires our proposals be produced in PDF, … Indeed, pretty much anything with mathematical content is authored in TeX, and turned into a PDF file.

Accessibility is not something we think a lot about. Until, that is, we run into some regulation (either Government or University) that mandates that the documents we produce be accessible to the blind or vision-impared. If you’re Australian or Canadian, you may already have run afoul of these demands.

Sooner or later, we all surely will …

Joe Clark to the rescue.

I won’t repeat all the main points of his article. Instead, what I want to concentrate on is mathematical text, and our PDF content-creation tools.

First of all, everyone is, or should be, using pdftex. There used to be issues with handling figures in pdftex. But that’s a thing of the past. And pdftex offers so many advantages over tex→dvips→ghostscript (hypertext links, bookmarks, alpha-transparency, …) that there’s really no good reason to use the latter.

One important feature for accessibility is “tagged PDF,” which was introduced with PDF 1.4. By default, pdftex outputs PDF 1.4, but it doesn’t produce tags. You can retrofit tags into PDF 1.4 documents using recent versions of Acrobat. But it would be better if pdftex had the ability to generate them natively1.

Accessibility of equations is something Joe didn’t touch upon at all, though he did allude to the shortcomings in the rendering of XHTML+MathML as a reason why they’re not going to replace PDF for mathematical texts anytime soon. But, whatever else you may say about it, MathML is accessible, and there’s at least one tool out there that will read MathML equations aloud. (Design Science received an NSF Grant for this effort, so, US readers, don’t think your Government doesn’t care about the issue.)

What about equations in PDF? Well, that’s the subject of another, more recent NSF Grant. What they plan to do, apparently, is embed MathML in the PDF file, and use the same technology, that allows their MathPlayer plugin to read MathML on the web, to read the MathML embedded in the PDF file.

MathML embedded in PDF … will some future version of pdftex support this? I don’t know. Ask Hàn Thể Thành. If not, there’s a serious possibility that, someday, you will be reduced to using MathType in Microsoft Word to produce accessible mathematical (PDF) documents.

1 There has been sporadic mention of tagged PDF on the pdftex mailing list but, as far as I can tell, no move afoot to implement it.

Posted by distler at August 23, 2005 1:22 PM

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Re: PDF Accessibility


Not only are we interested in having pdftex embed MathML in PDF for accessibility purposes, we want to enable embedding of TeX (and LaTeX …) as well. And, it is not only for accessibility purposes either. We hope to offer a free plugin for Adobe Reader (a sort of MathPlayer for Adobe Reader but we may not call it that when it ships) that interfaces with screen readers for accessibility, but also offers cut-and-paste of MathML and/or TeX into other apps and MP’s MathZoom facility. Finally, we hope to eventually make math in PDF (and HTML) searchable in a mathematically meaningful way.

We are hoping to engage the TeX community on this soon but your comment kind of demanded a response.


Posted by: Paul Topping on August 23, 2005 6:48 PM | Permalink | Reply to this

Embedding TeX in PDF

…we want to enable embedding of TeX (and LaTeX …) as well.

The open-source TeX world is already able to do that. Look at my previous post, where you can see this embedding facility in action in Apple’s Keynote (courtesy of LaTeXit, an open-source GUI wrapper around pdftex).

We are hoping to engage the TeX community on this soon but your comment kind of demanded a response.

Since, as I just pointed out, the TeX community is already doing some of what you have planned, it might be worthwhile to talk to them now, while you are in the planning stage, rather than later …

Posted by: Jacques Distler on August 23, 2005 7:23 PM | Permalink | PGP Sig | Reply to this

Re: PDF Accessibility

Anything new in the world of pdflatex producing accessible PDF’s? I am the manager at Connexions, where we use XML, MathML, and XSLT to create mostly accessible content online. But we use LaTeX and pdflatex to create printable PDF’s automatically from collected modules of educational material. At the XML level, we have the information needed to create tags, and alt text and proper encodings, but once transformed to LaTeX and then PDF (by pdflatex) we lose all that.

Just wondering if any progress had been made that we should be aware of.

Thanks for the nice blog entry.

Posted by: Katherine Fletcher on October 10, 2008 5:19 PM | Permalink | Reply to this

Re: PDF Accessibility

As I wrote a year later, there is (or was) a Working Group on PDF Accessibility, and I participated in a few of their Conference Calls, to give some input about mathematical content.

Alas, writing Standards is not quite the same as writing code. As far as I am aware, there’s been no progress on the pdfTeX front.

Since you’re auto-generating LaTeX from an XML source, you could use pdfLaTeX \special{}s and \pdfliteral{}s to pass information through to the generated PDF file. But (to my limited understanding), that would not suffice.

Posted by: Jacques Distler on October 11, 2008 12:24 AM | Permalink | PGP Sig | Reply to this

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