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When Simple Alt Text is Insufficient

By Barry Dahl – October 13, 2016

Fifth Blog Post in Series of Accessibility Tips for Online Teaching

[BROKEN LINK]In the previous post, I tried to explain the basics about Alt Text for images used in online courses. However, some images are far more complicated than others, and require much more alternative information than can be handled through normal Alt Text methods.

Complex Images

Complex images contain substantially more information than simple images. Describing a complex image requires more than a short phrase or sentence. Examples of complex images include, but are not limited to:

Numerical charts and graphs, flow charts, organizational charts
Diagrams and illustrations
Infographics or similar information-heavy graphics such as word clouds
Maps
Photos with a great deal of information that is important to the learning process

Long Descriptions

The Longdesc attribute is also an HTML attribute of the image, but it allows you to create or link to a web page in order to describe the importance of the image in more than the typical 100 characters allowed in standard alt text. The Longdesc attribute is not visible on screen, so that information is typically available only to students using assistive technology.¹

Let’s assume that the word cloud above is being used in a Baseball History class (it could happen) and that the information in the graphic is important for the expected student learning. Since it is an image, none of the text can be read by assistive technology. There is too much text for normal Alt Text, so Longdesc may be a good option. The LongDesc MLB Home Runs has been created and the link to that page will be included in the code for the image as shown below.

In Brightspace, there is not currently an easy way to enter a long description, so you would need to manually enter the longdesc attribute into the HTML code as shown above, and you would also need to create the long description web page that is being linked to.

In this example, on the long description web page, the student using the link provided in the long description tag will find all of the information contained in the image, including the names, number of home runs, and the date that the data was captured.

You may also consider linking to an audio recorded description if the instructor is loath to type out all the image long descriptions necessary.

Watch Karen Sorensen’s video on how JAWS reads the alt text and long description.

Data Tables as Alt Text for Charts

Data charts are usually not too difficult to display as tabular data. See how this pie chart can also be clearly represented as tabular data. The tabular data is real text, so it’s very accessible and provides an excellent alternate description for the chart image. Tables sometimes offer the ability to sort and interact with the data, so presenting the data in this way would definitely benefit all students.²

Pie Chart

The data table below contains the same information as the chart above, but because this table is made of real text, it can be read by screen reading software whereas the chart cannot be.

Property type	Percentage of Whole Property
Marsh	56%
Croplands	28%
Uplands	16%

A few final points about complex images:

Infographics have become popular for use in online courses because they are generally attractive and informative – as long as you can see them. It is possible to find infographics that are web accessible, but they are few and far between. Most infographics are a single image with limited or no alt text. Here’s a good example of an infographic that has readable text from the Washington Post.
Word clouds have found their place in online education, although they are often used primarily as eye candy. Unlike the example above, if the words, colors, or sizes of the words in the cloud are purely for decoration, then null Alt Text would be appropriate.

In the next post, we’ll look at finding captioned videos for use in online courses.

Accessibility Posts - October-November 2016

?Much of the content in this series of posts comes from WAMOE, the Web Accessibility MOOC for Online Educators; co-created by Karen Sorensen of Portland Community College and Barry Dahl of D2L.

¹Written by Karen Sorensen for WAMOE module 2-2.

²Written by Karen Sorensen for WAMOE module 2-5.