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Re: how to detect images having math expressions

for

From: Jukka K. Korpela
Date: Jun 4, 2008 4:50AM

Steve Green wrote:

> I would agree with that but manually visiting every page simply isn't
> practical for large websites.

That's why "accessibility testing" is a fairly impractical concept in
general. Alt tags are just a small part (very small part, really) of the
problem.

Pages should be _created_ and maintained so that they are accessible.
Testing them for accessibility is usually not useful, except when there
is a well-defined realistic goal (e.g., testing 0,1 % of the pages of a
large site to prove that the site needs a redesign).

> I was thinking that a more
> cost-effective option might be to assess all the images and identify
> those that may need non-null 'alt' attributes.

Can't be done, I'm afraid.

> When you find out
> which pages use these images it may mean that perhaps only 10% of the
> pages need to be assessed for that checkpoint.

How come? We might _guess_ that, say, 1 by 1 pixel images need alt="",
but that's just a guess, and such images are often symptoms of
accessibility problems that should be studied, instead of blindly
guessing that they are ignorable images. Besides, such images aren't
very popular these days, when formatting can be better achieved using
CSS.

I would say that even with a fairly sophisticated algorithm for
distinguishing "nullable" images from others, the percentage would
rather be 90 %, and what would be the point then?

Jukka K. Korpela ("Yucca")
http://www.cs.tut.fi/~jkorpela/