W3C home > Mailing lists > Public > public-apa@w3.org > December 2018

draft Accessibility Impact Statement for Filter Effects Module Level 1

From: Becky Gibson <becky@knowbility.org>
Date: Mon, 10 Dec 2018 17:54:47 -0500
Message-Id: <AAB7D231-E75F-429F-9AF9-4E6C0B172CE0@knowbility.org>
To: W3C WAI Accessible Platform Architectures <public-apa@w3.org>
I took a stab at a draft Accessibility Impact statement for the Filter Effects Module Level 1. I did my best to interpret the spec but I am no SVG expert!  I’m not sure if we need to worry about animations causing flashing?  I also did not list the Level AAA guidelines that might be affected:  
*1.4.6 Contrast Enhanced
*2.3.2 Three Flashes
*2.5.5 Target Size

And, on a brighter note, it may be possible to use filter effect to provide a mechanism to help meet 1.4.5 Images of Text by allowing customization which provides the exception, Customizable: The image of text can be visually customized <https://www.w3.org/TR/WCAG21/#dfn-visually-customized> to the user's requirements.”

Here is the actual draft to get us started: 

 The Accessible Platform Architectures (APA) Working Group requests addition of the following section to the specification Filter Effects Module Level 1 
https://www.w3.org/TR/filter-effects-1/ <https://www.w3.org/TR/filter-effects-1/>

Accessibility Impact Statement 

In addition to standard WCAG 2.1 requirements for images, content authors using filter effects should be mindful of how the filters modify the colors, contrast, size, and animation of images.  The following Level A and AA success criteria could be affected:

*Success Criterion 1.4.1 Use of Color (https://www.w3.org/TR/WCAG21/#use-of-color <https://www.w3.org/TR/WCAG21/#use-of-color>). Given a button shaped as an arrow with the text, “next,” a filter could modify the background color so that the text is no longer visible. 
*Success Criterion 1.4.3 Contrast (minimum) https://www.w3.org/TR/WCAG21/#contrast-minimum <https://www.w3.org/TR/WCAG21/#contrast-minimum>). Given the example above, a filter could modify the background or text color(s) so  color contrast requirement is not longer met.  
*Success Criterion 1.4.11 - Non-text Contrast (https://www.w3.org/TR/WCAG21/#non-text-contrast <https://www.w3.org/TR/WCAG21/#non-text-contrast>). Given the example above, a filter could modify the colors so that the contrast between the text and button color, and/or the button color and background no longer meet color contrast requirements. 
    It is particularly important to be mindful of color contrast  requirements when a transparency is present because automated measurement is not available to quantitatively and correctly judge whether sufficient contrast is being provided, thus requiring application of informed human judgement on a case by case basis.
*Success Criterion 2.3.1 Three Flashes or Below Threshold (https://www.w3.org/TR/WCAG21/#three-flashes-or-below-threshold <https://www.w3.org/TR/WCAG21/#three-flashes-or-below-threshold>)  Beware of any filters that add animation that may add or change the flash rate. 

Unfortunately I must offer regrets for the December 12 APA Working group meeting. Hopefully someone can perform a brief review of the Filter Effects Module to confirm (or not) my assessment. 

Received on Monday, 10 December 2018 22:55:11 UTC

This archive was generated by hypermail 2.3.1 : Monday, 10 December 2018 22:55:12 UTC