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Re: [css-color] incorrect contrast ratio calculation

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Mon, 16 Mar 2015 16:23:23 -0700
Message-ID: <CAAWBYDCBM+rWOLEWQ2g28qr7SqNvCPx4iN46uxEGYySCRaR_Zw@mail.gmail.com>
To: Andrew VanWagoner <thetalecrafter@gmail.com>
Cc: www-style list <www-style@w3.org>
On Fri, Mar 13, 2015 at 7:49 PM, Andrew VanWagoner
<thetalecrafter@gmail.com> wrote:
> Section 10.5 includes an incorrect formula for calculating contrast ratio:
>
> (L1 + 0.05) / (L2 + 0.05)
>
> where L1 is the smaller of the two luminances, and L2 is the larger.
>
> According to http://www.w3.org/TR/WCAG20/#contrast-ratiodef
> L1 is the *lighter* of the two, and lighter colors have a *larger* relative
> luminance (1 white, 0 black)
>
> so it should read:
>
> where L1 is the larger of the two luminances, and L2 is the smaller.

Fixed, thanks.

~TJ
Received on Monday, 16 March 2015 23:24:09 UTC

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