RE: 2.4 Proposed Modules - gpdf

[Bill Haneman <bill haneman sun com>]

Hi Jason!

As you know my concern about PDF 1.4 isn't so much about the structured
info as about the relationship between the structure and the rendered
view.  Not so important for blind users perhaps (if they don't
particularly want screen review) but very important for low-vision and
some other accessibility use cases; getting this "big picture" right
will require not only good content and PDF parsers that understand these
tags, but also communications between that layer and the rendering
canvas itself.

Simplest case in point is the need for glyph bounds info on the viewing
canvas and the means to connect that info back to the structured tree. 
I don't think the existing PDF canvases are smart enough for that, they
are IFAICT "write only" whiteboards that stuff gets painted onto.

It's probably a solvable problem though :-)

- Bill


On Fri, 2003-05-02 at 00:15, Jason White wrote:
> Owen Taylor writes:
>  > > 
>  > > I think the issue is with the formmat, namely that PS and PDF store lit-
>  > > tle (or no) structural information (eg, PS stores the position of indi-
>  > > vidual letters IIRC, but not the relationship between those letters).
>  > 
>  > There's quite a large amount of the PDF-1.4 spec related to trying
>  > to make the contents accessible. Whether 
>  > 
>  >  A) It is done in a useful manner
> 
> Yes it is - an entire structural tree, with elements and attributes as
> in an XML or SGML document can be represented in the PDF file. There
> is also provision for "text equivalents" to images etc., and various
> other useful features. Together these features are known as "tagged
> PDF" in the 1.4 specification.
> 
> XPDF, Ghostscript etc., don't implement these parts of the
> specification yet, which is a major obstacle to the implementation of
> support for PDF accessibility in Gnome or the Unix/Linux environment
> in general.
> 
>  >  B) Any content generators implement it
> 
> Adobe's authoring tools support it as of the latest versions (on MS
> platforms only).
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