Images and longdesc

[chris_fuel]

I was editing a page in Komodo Edit, and it has an accessibility feature to tell me when HTML might have accessibility issues. One of them it mentioned was to have a longdesc for the image. Now, I'm familiar with the alt-tag issue with images, but longdesc was fairly new to me. I looked it up with the w3 standards and got this:

longdesc = uri [CT]
This attribute specifies a link to a long description of the image. This description should supplement the short description provided using the alt attribute. When the image has an associated image map, this attribute should provide information about the image map's contents. This is particularly important for server-side image maps. Since an IMG element may be within the content of an A element, the user agent's mechanism in the user interface for accessing the "longdesc" resource of the former must be different than the mechanism for accessing the href resource of the latter.

I'm a bit confused on what it's trying to accomplish. There's 2 ways I'm interpreting this:

1. It links to a bunch of text that describes the image in more detail
2. It links to another page that describes the image through the page's contents and layouts (A sitemap image links to a sitemap)

The image I have is a logo, so I'm not quite sure what to make of this, as the examples the w3 gives is for sitemaps and imagemaps, not logos. Anyone that can shed some light on this?

[logic_earth]

As far as I know longdesc is pretty useless as nothing currently does anything with it. But you would use longdesc to describe an image like a photo a logo however doesn't fit this profile.

http://reference.sitepoint.com/html/img/longdesc

[AutisticCuckoo]

Unless it's very important to you to convey the exact appearance of the logo to a user who cannot see it, I'd recommend that you don't bother.

As Logic said, longdesc might be applicable for a photo or some other complex image that conveys lots of important information. Browsers don't support it at all, though, and I'm not even sure screen readers have much support for it. In any case, long descriptions are so uncommon that I'll bet few users are expecting them.

I do use long descriptions for the few photos on my blog, but I think the only 'visitors' to those description pages are search engine 'bots.

[Stomme poes]

A chart or a graph would be a perfect candidate for longdesc. The alt text would say, "Chart showing the company's performance in 2006" and the long desc would be all like, jan 2006 earnings were blah, feb 2006 earnings were blah, etc with a total increase of 57% over the course of thje fiscal year blah.... unless each month wasn't worth mentioning so then you'd use some other text, whatever's relevant like, the chart shows the largest increase in the month of August, which is the month we launched product B, showing its great success or whatever.

[AutisticCuckoo]

A chart or a graph would be a perfect candidate for longdesc. The alt text would say, "Chart showing the company's performance in 2006"

No, that's not a text equivalent, that's a caption. A more appropriate alt text would be, 'The earnings increased by 57% during 2006'. That is the information the chart conveys.

With images off, your proposed alt text wouldn't be of any help whatsoever to a user who cannot see the image. They'd just be frustrated because they'd know that there is a chart, but not what it contains.

My example gives them a summary, and a longdesc could provide more detailed information.

[Stomme poes]

They'd just be frustrated because they'd know that there is a chart, but not what it contains.

Why wouldn't they know what the chart contains? Isn't that the purpose of longdesc?
Or is longdesc only available to some surfers? (I've never seen it in action, but my understanding is that it's a link, right?)

*edit, nevermind, you said it doens't work in any browsers anyway.

[AutisticCuckoo]

Remember that alt texts aren't only for users who are blind and use a screen reader. They're also for people like me, who are restricted to a slow dial-up connection and surf with images off to make things bearable. We use ordinary browsers, which don't have any support for longdesc.

I see a lot of bad alt texts when I surf from home. One common error is to provide a description (caption) instead of a text equivalent, much like in your example.

Think about it: if you couldn't see the chart, would you rather know that there is a chart but not what information is in it, or would you rather get a summary of the data?

[Stomme poes]

So far, I've limited myself to having all relevent content in the text at all times. To me, images are pretties, but I am indeed about to embark into the world of mortgage pages (gawd no) which have images that actually say something for the first time. This will probably be in about a month. My plan was the usual alt text (which I know you want blended into the text but I never do because it looks confusing on my browser, which doesn't mark anything off as an image so I get this weird text in the middle of a paragraph that sounds like a sort non-sequitor if I'm not careful) with the option to click for an actual play-by-play of the chart (depending on what the chart's doing... so far the one I've used seems to say nothing and was chosen as decoration to make the site look... mortgage-y, as in there are no numbers on it!) preferably on a seperate page. This is what I thought long-desc was. If it's not, I'm going to have a caption/link mix.

I don't write the content (I convert the old pages) so that makes me more limited. I don't want to hear an introductory paragraph on mortgages with then a sudden and quite detailed explanation coming out of nowhere about a particular mortgage (as if I'm floating an image it may be HTML'd between an intro paragraph and a paragraph about one type of mortgage, which it sits alongside). At the very least, I'd want to hear that after the paragraph explaining the basics of that kind of mortgage. Then I want to be told that I'm about to hear a detailed example of what was just explained, which I could skip if I want.

So if this (in the other example) was good alt text: 'The earnings increased by 57% during 2006', then it really limits where I can stick that image in the HTML, because that sentence doesn't go with the paragraph that the image is hanging out with. It might summarise the paragraph or something, but I don't want to hear it in between normal sentences as it is confusing and sounds strange. It looks strange too, on my browser. I've even started sticking [brackets] around my alt text so I can tell it's alt text, after someone else showed them to me.

I'll be definitely finding out more about what the options are as I begin to wade into this.

[AutisticCuckoo]

If the alt text doesn't fit it with the paragraph, it's probably the wrong alt text.

The best way – which isn't always possible – is to write the text first, and then replace part of it with an image. The replaced text will then be the alt text.

Writing good alt texts is tricky and takes practice.

[Stomme poes]

Heh, I'll be getting plenty of that.

Something like "Earnings grew 57% in 2006" reminds me of magazines where the caption under the photo was really a summary of, usually, the article, or some large point made in it. When I read magazine, I skip or block out the images, and when I get to the end of the article I go back and look and read the captions, because they usually break my reading flow (or sometimes I read them first). For instance I once read a one-page article in TIME about Enron, where the majority of the article went over the fall of Enron and how the employees were some of the hardest hit. The single image in the article was about half-way down, and showed some people sitting in front of the big E that was a sort of statue in front of the company headquarters. The caption said something like, "Enron employees and retirees are hardest hit by the scandal." I then assumed the people sitting in front were employees, though I'm not sure. But it was something that I didn't want to read in the middle of more detailed info.

For something that requires a few paragraphs of explanation (like how a particular example mortgage works), will have to take a lot of thinking and planning.
For a replacement of long-desc, what do you think of a "caption" under/next to the photo that's also a link to a page which describes in detail the chart (listing every month or year and how the different numbers change)? People could then have the option to click and learn more, or they were only reading the page to get a general idea of the different types and could skip the detailed examples.

[AutisticCuckoo]

A common solution used to be to put a [D] link near the image, like a poor man's longdesc. The link would go to a page with a description of the image.

This seems to have gone out of fashion these days, but you could use a similar principle (perhaps using a more descriptive link text).

[Stomme poes]

A [D] link? I've never heard of that. I'll check it out.

[AutisticCuckoo]

It used to be common in the '90s. The W3C specs contains a few, IIRC.