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Re: how to detect images having math expressions

for

From: Christophe Strobbe
Date: Jun 4, 2008 5:00AM

Hi,

At 12:15 4/06/2008, Steve Green wrote:
>I would agree with that but manually visiting every page simply isn't
>practical for large websites. 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. 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.
>
>Once you get above a few hundred pages it becomes impossible to test every
>page for every checkpoint.

You need a good sampling method when evaluating large sites.
In Europe, the WAB Cluster researched this (with a lot of input from
EIAO, one of the three WAB Cluster projects). See Chapter 4 (Scope and
sampling of resources) in the "Core" section of the Unified Web
Evaluation Methodology (UWEM) at
<http://www.wabcluster.org/uwem1_2/>;. Section 4.3.2 discusses automated
sampling.


>It is not cost-effective (and may not even be
>possible) to do it manually, and automated tools only do a very small part
>of the job. I am interested in techniques that make better use of the
>available manual resources to do things that automated tools cannot do at
>all, when a brute force (i.e. view every page) approach is not an option.

There are open-source libraries for OCR (<http://jocr.sourceforge.net/>;)
but I am not aware of efforts to use them in accessibility evaluation
tools (not even rough classification).

Best regards,

Christophe



>Steve
>
>
>
>-----Original Message-----
>From: <EMAIL REMOVED>
>[mailto: <EMAIL REMOVED> ] On Behalf Of Jukka K. Korpela
>Sent: 04 June 2008 10:48
>To: WebAIM Discussion List
>Subject: Re: [WebAIM] how to detect images having math expressions
>
>Steve Green wrote:
>
> > It would probably be more cost effective and reliable to produce a
> > list of all the images and have someone (this need only be a very
> > cheap resource) look at them all and flag any that contain text or
> > math expressions.
>
>It would be even better to ask a human tester to evaluate all images for
>accessibility. Texts that contain text or math are just a special case, and
>it's probably better to work out all images in one pass. They should of
>course be evaluated in context, since it is generally impossible to judge
>what is an appropriate alt text just by looking at the image. (For example,
>an image might be purely decorative, calling for alt="", in some context,
>and a content-rich image requiring a longish textual alternative in
>another.)
>
>Jukka K. Korpela ("Yucca")
>http://www.cs.tut.fi/~jkorpela/

--
Christophe Strobbe
K.U.Leuven - Dept. of Electrical Engineering - SCD
Research Group on Document Architectures
Kasteelpark Arenberg 10 bus 2442
B-3001 Leuven-Heverlee
BELGIUM
tel: +32 16 32 85 51
http://www.docarch.be/
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