Resources for Writing Image Descriptions
Image descriptions greatly increase the accessibility of the image content in NIMAS files, and the NIMAC welcomes publishers to supply alt text for their files.
Alt text is not required by the NIMAS specification. However, if it is supplied, it must be of good quality. This means it should be clear, appropriate for the grade level, and grammatically correct. We strongly recommend that alt text be provided by the publisher.
Here are some guidelines to get you started:
- Alt text should be short–no longer than 1-2 sentences.
- If you would also like to include a longer description for more complex images, the <prodnote> tag can be used for this purpose.
- If a caption already provides a good description of the image, the alt text attribute can be left empty. (A caption should not be repeated as alt text.)
Below are some resources that provide further guidance on how to write good alt text for your materials.
Web Accessibility Tutorials: Images Concepts
The Web Accessibility Images Tutorial is an incredibly in-depth resource from the Web Accessibility Initiative, covering how to provide alt text for seven different types of images. The introduction/overview features brief descriptions of each image type to help the user decide which section they should view in more detail. Each section of the tutorial includes several examples with snippets of code and some examples incorporate MathML. At the end of each section is a list of Related WCAG Resources that users may find useful.
DIAGRAM Center Image Description Guidelines
The DIAGRAM Center/Benetech Image Description Guidelines feature a linked table of contents along with both general and subject specific image description guidelines. Examples are provided for both elementary and secondary level students.
DIAGRAM Center Image Description Examples
The sample book of image descriptions, also from DIAGRAM/Benetech, includes numerous examples of how to write alt text and how to code it in DAISY and MathML.