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RE: Color contrast principle

From: Alastair Campbell <acampbell@nomensa.com>
Date: Wed, 16 Jan 2019 18:04:03 +0000
To: "WCAG list (w3c-wai-gl@w3.org)" <w3c-wai-gl@w3.org>
Message-ID: <AM5PR0902MB2002CEE53C55811042EE0306B9820@AM5PR0902MB2002.eurprd09.prod.outlook.com>
Hi everyone,

Busy day, just catching up, some comments before a suggestion:

JonA wrote:
> an adjacent point that is not immediately touching the initial point can be used for the comparison when the sum of corresponding points communicates the same information needed to identify parts of the control or graphic and its states.

I see where you’re going, but I’m wary of the ‘not immediately touching the initial point’ aspect, I think a concept about combining / merging areas would be more effective.


Detlev wrote:
> it is important to allow cases where (thin) outlines can be disregarded if the colours they separate have enough contrast between them. It might be necessary to define the upper limit of the line thickness though, in some way, not sure how  (3 or 4 CSS pixels? Could appear arbitrary.)

I’m not sure that it matters how thick it is, If something were a thick, non-contrasting border it is considered merged. It would be very difficult to bring in a concept of thickness at this stage, we need to base it more around “Visual information required to identify user interface components”.


How about replacing the paragraph above the second example in Adjacent colors with:

If components use several colors, any color which does not interfere with identifying the component can be ignored for the purpose of measuring contrast ratio. For example, a 3D drop-shadow on an input, or a dark border line between contrasting backgrounds can be assumed to merge into the color closest in luminance.

The following example shows an input that has a light background on the inside and a dark background around it. The input also has a dark grey border which can be assumed to merge into the dark background. The border does not interfer with identifying the component, so the contrast ratio is taken between the white background and dark blue background.

Does that make sense to people?

It’s hard to describe this simply, reading other people’s attempts makes my head spin so I assume that’s what I’m doing to everyone else, sorry!

Cheers,

-Alastair
Received on Wednesday, 16 January 2019 18:04:31 UTC

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