“A text equivalent for every non-text element shall be provided (e.g., via “alt”, “longdesc”, or in element content)” – §1194.22(a)
Ranging from photographs to charts, graphs and mathmatical equations, images are frequently placed in PDF documents to convey information.
EXAMPLE: A page contains an image of a company logo.
RESOLUTION: Provide an associated text description that pronounces the company name followed by “logo” or “icon” as appropriate.
For those who read with assistive technologies a description of the graphic object is often the only access to the content.
What’s different about PDF?
This requirement is among the most familiar in terms of basic accessibility needs. However, in PDF there are three additional considerations.
- In PDF we have a class of graphical objects known as “artifacts”. Artifacts are distinguished from “content” images because they simply provide cosmetic effects rather than information. Artifacts must be marked as such.
- In PDF we must distinguish between “Alt text”, which describes the contents of a Figure tag, and “Actual text” which simply replaces the contents of a Figure tag. An example of this distinction is given below.
- In PDF we often see many smaller graphics that must be grouped together under the same Figure tag in order to make up a single graphic for alt. text purposes.
What happens when I verify this Checkpoint?
The window allows you to add or modify alt and actual text settings for each tagged Figure, indicate whether the alt text quality is adequate and add comments for other remediators as necessary.
The upper window allows you to review and make changes to the actual text and alternate text settings of each non-textual element of the current page.
As you select a row in the upper portion of the window, the corresponding non-textual element is displayed in the lower window.
When to Pass or Fail this Checkpoint?
|Pass||If the Alt text or Actual text is appropriate.|
|Fail||If the alt text requires additional review or correction outside of this remediation session.|
|Remediation||Update the Alt and/or Actual text fields to properly describe the figure or provide replacement text.|
|Comments||You may include comments for any figures marked as Failed. These comments appear in the Results window and final verification report.|
Once “Ok” is clicked, any changes to actual or alternative text are permanently saved to the PDF document.
In the example the “T” in “The” is an image.
The correct method for text tags in this instance is: Actual Text = T, Alt Text is blank. The screen reader will then read ‘the’ correctly.
The incorrect method for text tags in this instance is: Actual Text = blank or T, Alt Text =T. The screen reader will then read ‘t he’. The ‘t’ sound will be followed by the ‘he’ sound.
If both the Alt Text and Actual Text fields contain values (which isn’t recommended), Alt Text will probably override ActualText when read by assistive technology.
This checkpoint is partially automated. It displays for any page that contains non-textual elements.