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Re: Suggested addition to 1.1

From: Charles McCathieNevile <charles@w3.org>
Date: Sun, 11 Feb 2001 21:12:00 -0500 (EST)
To: Marti <marti@agassa.com>
cc: Anne Pemberton <apembert@erols.com>, <w3c-wai-gl@w3.org>
Message-ID: <Pine.LNX.4.30.0102112059210.32476-100000@tux.w3.org>
Some thoughts:

Providing the small image as a link to a larger one (when the image is used
as an image, not a link to something else), is a good thing to do. Where the
link to the larger version of the image appears, there should also be textual
equivalent information. Some of this might be "inline" such as the HTML alt
attribute, and some of it might be via a link, such as the HTML longdesc

This is how to meet the requirement that someone reading a page can find out
what is on the page.

For an image itself, there are actually techniques for including alternative
information directly in the image.

There is a W3C Note (Describing and retrieving photos using RDF and HTTP) and
an associated set of free software that explains how to include all kinds of
information, including a title, authoring information, a description, links
to recorded-audio description, and so on in a jpg file, and how to get it out
again. The same principles can easily be applied to PNG and GIF formats, but
the tools developed do not currently handle those formats. The Note is at

For SVG images, there are a range of techniques that can be used, and another
W3C Note (Accessibility features of SVG) that describes how to use them. That
Note is at http://www.w3.org/TR/SVG-access (and is in the intial stages of
being revised and updated)

And for multimedia stuff like movies there is a whole raft of work available.

The Authoring Tool Accessibility Guidelines has requirements that tools use
this kind of information to help authors by proposing equivalents, and that
they acutally help authors to produce images that include it. If people asked
about ATAG conformance when they are looking for image-processing software as
well as looking for software that could take advantage of this in authoring
Web pages, it would encourage the companies who are already making efforts in
that direction.


Charles McCN

On Sat, 10 Feb 2001, Marti wrote:

  > How does this simple and elegant solution to minimizing image downloads to
  > users  pose a problem for disabled human users? Seems to solve the problem
  > of low vision users who want to see the picture at their use level, make
  > the picture available to be printed easily, and allows the use of detailed
  > photos to illustrate the page.
   I am not sure I understand what you are asking about here? If you mean the
  link directly to an image file that I said could be a violation, I think you
  answered the question yourself, there is no way to attach alt or longdesc
  information if you do that. On the other hand, you can wrap some very simple
  html arond it and allow the alt information.
  In a way, linking directly to an image file is like linking to a PDF
  document which has been created as just an image.

Charles McCathieNevile    http://www.w3.org/People/Charles  phone: +61 409 134 136
W3C Web Accessibility Initiative     http://www.w3.org/WAI    fax: +1 617 258 5999
Location: I-cubed, 110 Victoria Street, Carlton VIC 3053, Australia
(or W3C INRIA, Route des Lucioles, BP 93, 06902 Sophia Antipolis Cedex, France)
Received on Sunday, 11 February 2001 21:12:14 UTC

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