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Re: Discussion on Change Proposal for ISSUE-66

From: Shelley Powers <shelley.just@gmail.com>
Date: Fri, 22 Jan 2010 09:17:55 -0600
Message-ID: <643cc0271001220717rc478f7cxaae2671e8ca688ab@mail.gmail.com>
To: Lachlan Hunt <lachlan.hunt@lachy.id.au>
Cc: Maciej Stachowiak <mjs@apple.com>, Matt May <mattmay@adobe.com>, HTML WG <public-html@w3.org>, public-html-a11y@w3.org
On Fri, Jan 22, 2010 at 4:52 AM, Lachlan Hunt <lachlan.hunt@lachy.id.au> wrote:
> I've had a go at writing a proposal for some alternative spec text to
> resolve this issue.
> ---
> When the user is unable to make direct use of the image, e.g. due to a
> visual disability or because they are using a text terminal with no graphics
> capabilities, user agents may also provide the user with the ability to
> obtain any other information about the image that may assist the user in
> understanding its content or purpose, utilising any available repair
> technique.
> Such techniques may be based on information from any relevant source
> including, but not limited to, the following suggestions:
> * Obtaining the file name from the URL reference or HTTP headers
>  supplied with the resource, such as the Content-Location or
>  Content-Disposition header fields.
> * Extracting human readable metadata embedded within the resource.
>  e.g. EXIF, RDF or XMP.
> * Referring to alternative text associated with another instance of the
>  same resource on the page.
> * Applying OCR techniques to recognise and extract textual content that
>  is graphically represented on the image.
> For more information, refer to the User Agent Accessibility Guidelines
> techniques for repairing missing content ([UAAG10-TECHS], section 2.7).
> ---
> (Note that the first 3 techniques listed above are based on the techniques
> listed in UAAG)

Oh, and a quick PS: Most paint programs have an "export to the web"
functionality that strips out much of the metadata, and other data
that can be mined. Rightfully so, as most of this is mineable by the
paint programs, and not intended for general web use. You really can't
count on this data.

As for generating alternatives, most software such as CMS use these
techniques anyway, it isn't necessary for the UAs. It's more efficient
if the authoring tools derive this information once, then it is for
UAs to generate it every time the image is viewed.

Luckily, authoring tools also make it easier to add the alt text.
What's needed is clear directions in the spec that this text should be
supplied, and meaningful.

> --
> Lachlan Hunt - Opera Software


> http://lachy.id.au/
> http://www.opera.com/
Received on Friday, 22 January 2010 15:18:30 UTC

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