RE: Color contrast of text on variable color background

I agree with Lea Verou that there should be guidelines for this and
agree with John Foliot’s comments in support of her point-of-view.

In the absence of such guidelines, my concern is that designers will,
rightfully, continue this practice but do so favoring aesthetics over
readability. I’m afraid the visual presence of the entirety of an
image is valued more highly than easily reading any overlayed text.
With or without guidelines designers may do what they wish but an
objective, authoritative guideline would give a forceful counterpoint
to “it looks better” and help move inclusive design forward..

In a responsive layout, it can be difficult to predict what part of an
image text may interact with—and the text may change. Therefore, the
contrast ratio over the entirety of an image should be considered.

An objective measure could be achieved as follows:
1) current WCAG contrast ratio minimums must be met
2) calculate contrast ratios with the overlaying text of the lightest
and darkest areas of the image
3) the difference in contrast ratios between the lightest and darkest
areas should fall within a specified range, limiting variation

The range could be a fixed number or calculated on a sliding scale
depending on contrast ratio values or both.

Received on Thursday, 27 June 2019 02:51:08 UTC