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Re: Color Contrast List?


From: Jared Smith
Date: Apr 29, 2013 12:31PM

On Mon, Apr 29, 2013 at 11:42 AM, James Nurthen wrote:

> - Background images under text

If a user disabled images, it is important that a background color be
defined that provides adequate contrast for the text. It is my opinion
that contrast tools should flag contrast issues regardless of whether
a background image is defined or present.

At the same time, it would be helpful for contrast tools to also check
for issues with background images, but this is quite difficult to do
in an automated way, especially if the image contains both the
foreground text and the background color.

> - CSS Gradients

Yep. This is also quite difficult to do in an automated tool due to
the many complex ways in which gradients can be defined. There also is
no specification in WCAG as to how to handle gradients (or text
highlights, drop shadows, borders, rgba, etc.)

> - Any background CSS colours using rgba values (semi-transparent
> backgrounds)

WAVE accounts for semi-transparency though there is no defined WCAG
formula for doing so. Again, this is fairly complex to handle and we
need to refine this.

> These techniques are becoming more and more common so these semi-automated
> tools are becoming less and less useful over time.

Which increases the necessity for common sense and manual testing,
though I realize the limitations for blind users in manual testing
these visual components.