Images in Canvas need accurate descriptions for students who rely on screen readers. Images that convey a lot of text should be avoided whenever possible, and descriptions should be presented to provide enough information within context of the topic. Keep in mind the context of the picture, which may change the scope of the needed description.
Image context will change based on the audience and what you want them to learn about the image. The same image could have different descriptions depending on its intent. If you are creating the course or the content, remember that you are the artist and you get to pick the alternate text.
For more guidance on using alt tags, please see the Diagram Center’s Poet Training Tool
Diagrams and Charts
Alternate text for diagrams and charts can be accomplished but its possible these items might be better represented in a list or a table structure. Complex graphs and charts can include an over load of information.
Diagram and Chart Example
Convert diagrams and charts to tables
Adapted from DiagramCenter
Bonus Video on accessible bar charts
- Bar graphs should be converted into accessible tables.
- Briefly describe the graph and give a summary if one is immediately apparent.
- Provide the title and axis labels.
- It is not necessary to describe the visual attributes of the bars, e.g. dark blue, light blue, unless there is an explicit need such as an exam question referring to the colors.
Figure 1 is a bar graph that measures percentage of vaccination coverage in five states over one year, from Q3 2006 to Q2 2007. In each state, the coverage increases over time. The data are summarized in the following table. All data are approximate.
First dose rotavirus vaccination coverage among children aged 3 months, by quarter – immunization information system (IIS) sentinel sites, United States, 2006-2007.
|Arizona||District of Columbia||Michigan||Minnesota||Montana||Oregon|
Things to consider with alternate text and images in Canvas
- Avoid “picture of” or “image of”
- Avoid having the file name as the alt text – this will sometimes not show up in the accessibility check
- Imagine explaining the picture over the phone to someone and use that as the alternate text.