Michael Gaigg: Über UI/UX Design


Best Practices for accessible Images

Graphics can be of great benefit to the accessibility of a Web page by providing

  • Illustrations
  • Icons
  • Animations
  • other visual cues that aid comprehension for sighted individuals

When designing for people with disabilities too often we forget that we are not designing only for the blind. We must consider disabilities of all types. Graphics can be useful especially to individuals with certain reading disabilities, learning disabilities, attention deficit disorders, or cognitive disabilities.

Basic Rules

  • Do not use color alone to convey meaning
  • Choose contrast so that text is easily distinguishable from the background
  • Communicate the purpose of the graphic (not its appearance) through meaningful alternative text
  • When graphics require complex descriptions use the longdesc attribute, a link to an alternative page, a description in the context itself, or a “D” link
  • Use empty alt text for decorative, transparent, spacer, and redundant images
  • Try to limit the amount of text in graphics
  • Do not use effects that flicker or produce a strobe-like effect
  • Use images as backgrounds only if they do not convey important content (since it is impossible to add alt text to background images)

Best Practices

Level 1

Level 1 Checkpoints - Section 508 Compliancy Standards
Description W3C 508 Example
Ensure that all information conveyed with color is also available without color 2.1 c Ensure that information is available through other style effects (e.g., a font effect), through context (e.g,. comprehensive text links) or through mark-up (e.g., the title attribute).
Until user agents allow users to control flickering, avoid causing the screen to flicker 7.1 j n/a
Provide text equivalent for Images, graphical or animated buttons, spacers, bullets 1.1 a <FORM action="..." method="post">

  <INPUT type="button" alt="Click this button to verify form" value="Verify" onclick="verify()">

  <INPUT type="image" name="submit" src="button.gif" alt="Submit form">


Level 2

Level 2 Checkpoints - Section 508 Compliancy Standards
Description W3C 508 Example
Ensure that foreground and background color combinations provide sufficient contrast when viewed by someone having color deficits or when viewed on a black and white screen 2.2 c For more information check the online paper about Effective Color Contrast.
When an appropriate markup language exists, use markup rather than images to convey information 3.1 n/a Mark up complex equations with e.g. MathML.
Avoid causing content to blink 7.2 n/a n/a
Avoid movement in pages 7.3 n/a i.e., hide/show content or change presentation (movement and colors).

Level 3

Level 3 Checkpoints - Section 508 Compliancy Standards
Description W3C 508 Example
Supplement text with graphic or auditory presentations where they will facilitate comprehension of the page 14.2 n/a n/a


Similar Posts:

Posted by Michael Gaigg

Comments (0) Trackbacks (0)

No comments yet.

Leave a Reply

No trackbacks yet.