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RE: high contrast and background images

From: Jonathan Avila <jon.avila@ssbbartgroup.com>
Date: Tue, 15 Jun 2010 09:11:10 -0400
Message-ID: <1dfaac7617f1d8025219f0fac3bee08d@mail.gmail.com>
To: ng@tjkdesign.com, w3c-wai-ig@w3.org
Thierry Wrote:
"A better approach would be to ... avoid losing these images when users
switch to high contrast styles sheets."

Actually, converting images of text to text would be good for many low
vision users.  The WCAG 2 Level AA success criteria indicates that images
of text should not be used unless essential or the technology does not
support.

Your point is well taken for images that are not text.  However, I do have
several thoughts.  Since only one image is used, automated testing tools
will need to pull the viewport coordinates from the code to determine
which area of the larger image is applicable to the current element.  For
instance, an automated testing tool displays the whole image when needed.
In the example from
http://tjkdesign.com/articles/how-to_use_sprites_with_my_Image_Replacement
_technique.asp text is used since this is a heading where text fits.
However, many sites that use this technique will likely use icons where
there is not sufficient room to place on-screen text without messing up
the layout.  In those cases alt text would need to be applied to the image
and I'm sure some developers won't do this.  When an automated tool
detects the missing alt text it will display the entire image for the user
to review to determine what the appropriate alt text is.

The example also uses a lot of fixed pixel coordinates.  I am unclear if
relative sizing can be used effectively with this solution.

Jonathan
Received on Tuesday, 15 June 2010 13:11:45 GMT

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