[whatwg] ALT and equivalent representation

[Philip Taylor]

On 18/04/2008, Bill Mason <whatwg at accessibleinter.net> wrote:
>  The example was a case of a hacker who replaces the Google logo on
> google.com with an image only containing the text "WE HACKED YOUR SERVERS".
> We assume the hacker cares enough about accessibility to set the alt
> attribute to the same text.

More generally (and less hypothetically), this is any case where an
image is being used just to display text (in a nicer font, or nicer
colours, or animated and on fire, or some other reason it's worth
using an image instead of plain HTML).


>  Since the image is no longer the company logo, it falls outside the logo
> discussion in the Icons requirement for alt.

I believe the company logo case is also unclear in the spec. See e.g.
http://www.google.com/ (when it's not a special day) - the image is
simply the word "Google" (as a page heading, so it should probably be
in <h1>), so common sense says it should have alt="Google". The spec
phrase "Icons: a short phrase or label with an alternative graphical
representation" sounds like it might apply here, but none of the cases
in that section seems to work: in particular, I don't think "the logo
is being used to represent the entity" would apply, because the
purpose of the image is not to represent the entity (as it would be in
e.g. a list of search engines that shows small images of all their
logos so you can choose your favourite), and instead its purpose is to
tell users what site they are on (and to make it look prettier). It
should be made clearer whether the existing case does or does not
apply. If it does not apply, it should be made clear what alt text to
use instead.


Since we're on this topic...


What should happen for 'tracker' images? (i.e. <img
src="http://evil.google.com/user-track.php?site=97519340" width="1"
height="1" alt="???">)
As some examples, Geocities has alt="setstats", someone has
alt="statystyka", someone has alt="CrawlTrack: free crawlers and
spiders tracking script for webmaster- SEO script -script gratuit de
détection des robots pour webmaster", etc, and those examples do not
help users who are seeing the alt text.

Such images are pretty common, and they're not going to go away, so we
should minimise their harm by saying alt="" is appropriate. None of
the cases in the spec seem to cover this case yet.


http://validator.nu/?doc=http%3A%2F%2Fwww.google.com%2F&showimagereport=yes&showsource=yes
shows that some versions of Google (depending on cookies, IP address,
etc) implement the "Google" logo as four separate images,
approximately like:

.------.-.----.
| G o o|g|l e |
'------+-+----'
       '-' Suomi

where the "Suomi" (text, not image) is adjacent to the g's descender.

The "Goo" image has alt="Google", and the other three images have
alt="". When the page is viewed without images, that means it will say
"Google" instead of the logo, which is a good thing. But HTML5 says
that the alt text is equivalent to the image, which is not true (and
could only be satisfied by alt="Goo", alt="le", alt="Most of a g",
alt="A little bit of a g", which would be silly) - in this case, it is
the combination of alt texts on the whole page that is equivalent to
the combination of images on the page.

google.com is splitting the image up to fit it in a layout table,
which is non-conforming HTML5; but there are other more legitimate
reasons for having several img elements representing a single piece of
text, and in those cases it seems sensible to put alt="all the text"
on one image and alt="" on the others. Should HTML5 be changed to
accept this?


And as a more general point, the spec provides a list of cases for
using img (and how to use alt for those cases), but this list will
never be complete (especially since the case matches are all
subjective and open to interpretation in multiple ways), so there
needs to be a default case statement for images where the author
doesn't think any of the specific requirements applies.

-- 
Philip Taylor
excors at gmail.com