WebAIM - Web Accessibility In Mind

E-mail List Archives

Re: Chrome color contrast analyzer Pixel radius

for

From: Cliff Tyllick
Date: Jan 4, 2016 12:18PM

I don't know, but I am curious to know more about this concept.

I have known designers to try to make contrast adequate by adding a 1-pixel-wide high-contrast color between foreground and background. I doubt that actually helps. I've been told it actually hinders every sighted person from perceiving the border quickly and correctly. But your results don't seem consistent with a test of this approach. In this case, the value for 1 pixel radius would be higher.

On the other hand, we have dithering, which uses intermediate colors to smooth the appearance of an edge that otherwise would seem to be pixelated. It seems like this would give rise to the results you obtained. If so, I would hope that the answer is that the contrast is adequate.

But, yeah, I'd like to know more about this algorithm in particular and these aspects of adjusting contrast and improving legibility in general.

Cliff Tyllick

Sent from my iPhone
Although its spellcheck often saves me, all goofs in sent messages are its fault.

> On Jan 4, 2016, at 11:11 AM, Alan Zaitchik < <EMAIL REMOVED> > wrote:
>
> Anyone know the answer to this one?
> Using the Google Chrome color contrast test there is an option to set the "pixel radius" to 1, 2, or 3.
> Anyone know which value to use under which circumstances? I have pages that fail with radius 1 but pass with radius 2.
> Is this bad or not?
> A
>
> > > >