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Create images available long description
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Warning: the original version of this document is Creating Accessible Images: Long Descriptions . This French translation was done by Ideos under an agreement between WebAIM and Ideos .
Note: See page documents on web accessibility for a list of all translated documents. Other resources on web accessibility are also listed in the digital portal accessible .
Summary
- Page 1: Introduction
- Page 2: Images to enhance understanding
- Page 3: Color and Contrast
- Page 4: Texts in pictures
- Page 5: The graphs that cause spasms
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Page 6: Creating good text alternatives (attribute
alt) - You are on Page 7: Long Descriptions
When to make a long description?
In some cases, an image is too complex to describe in few words.
Tables and graphs are the main examples of such images.
Although there is no limit to the length of the text in an attribute alt , the alt text is to be relatively short.
It would be an abuse to write more than a few words or even a few short sentences.
So the answer is to give a short text alternative in the attribute alt and provide a more detailed way.
Methods to create a long description
There are several ways to give a long description to images. These opportunities are listed below that most preferred to the least preferred:
- Put a long description in the context of the document itself.
- Put a link to the long description for link text.
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Put a link to a long description via attribute
longdesc. - Put a link to a long description with a link "d" link.
Those familiar with the techniques of accessibility may be surprised to see the attribute longdesc link and "d" link at the end of the list.
The reason is that both approaches are problematic.
The attribute longdesc is invisible (and inaccessible in some browsers) for people who do not use modern screen readers.
The "d" link is a link unconventional.
It can be confusing for people who do not know.
The easiest way to make available long descriptions is to make them visible and available to everyone, whether disabled or not.
In the body of the document
By a long description in the body of the document where there is the image, everyone benefits, not just the disabled. Everyone will be able to read the long description and benefit. Here's an example embodiment with an image of a graph:
The chart above shows the percentages of the total non-institutional U.S. aged 16-64 years reporting one or more disabilities. The values of the percentage in each category are:
- Total persons reporting one or more disabilities: 18.6%
- Sensory disability (visual or auditory): 2.3%
- Physical disability: 6.2%
- Mental disability: 3.8%
- Self-care: 1.8%
- Difficulty leaving home: 6.4%
- occupational disability: 11.9%
The data is extracted from the document US Census 2000 (pdf, 880 kb) .
In the example above, the data appears after the image and are accessible to all.
A normal text link
The second best way to provide a long description is simply to put a link to a text. There is no specific code or specific technique to use here. Just put a link to a long description, as in the example below:
The textual description of the chart is available on another page.
Information is available to everyone by this method also, even if we click on a link to it. The link is visible to all. You can choose to click or not.
The attribute longdesc
The attribute longdesc , which can be added to a tag img , does nothing more than to provide a link to a page where a long description is available.
It works the same way as in the previous example, except that the link is invisible to sighted readers.
The following example is the same graph with an attribute longdesc added:
Include those who see that there is nothing visible when the attribute longdesc is used.
In their case, it is as if he were not there.
The only people who can access the attribute longdesc are those that use modern screen readers.
Screen readers do not interpret the older attribute.
Even among those who use the latest version of their screen reader, there are many who are not familiar with the attribute longdesc (because it is so rarely used) and do not know how to access it, even if the reader The screen supports.
The key point is that the attribute longdesc only benefits a small number of people, despite the fact that it is a technique recommended in both the recommendations of the WAI and Section 508.
Here is the code for the attribute longdesc :
The links "D" ("D" Links)
Before the tag longdesc is supported by screen readers, a group of people decided they needed an equivalent method that is supported by browsers.
They then invented the link "d".
The letter "d" means "description".
These links "d" are actually links that point to other pages which link is the title of the letter "d".
Here is a link would look like "d" in our example:
You can use a capital D or small d. It's not really important. A link "D" is usually placed right after the image. This technique works in all browsers, it fulfills its objective of providing a textual description but is less elegant than other methods. Some people will be confused by a link whose title is a single letter. Others will simply ignore it. You can use this method, but only if you have a good reason to reject the other.
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