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Re: Alternative Style Sheets

From: Gérard Talbot <www-style@gtalbot.org>
Date: Sat, 13 Oct 2012 22:21:34 -0400
Message-ID: <5d93783e20355ba2adc8b2e25a910971.squirrel@ed-sh-cp3.entirelydigital.com>
To: "Antony Kennedy" <antony@silversquid.com>
Cc: "Markus Ernst" <derernst@gmx.ch>, "www-style@gtalbot.org" <www-style@gtalbot.org>, "Dirk Schulze" <dschulze@adobe.com>, "www-style@w3.org" <www-style@w3.org>

Le Sam 13 octobre 2012 5:41, Antony Kennedy a écrit :
> More than that, there is no colour scheme that will satisfy all
> requirements. Even if you follow WCAG guidelines.
>
> Sent from my iPhone

Anthony, I respectfully disagree with you.

"
Checkpoint 2.2 - Ensure that foreground and background color combinations
provide sufficient contrast when viewed by someone having color deficits
or when viewed on a black and white screen
Technique 2.2.1 [priority 3] Test the color attributes of the following
elements for visibility:

Two colors provide good color visibility if the brightness difference and
the color difference between the two colors are greater than a set range.

Color brightness is determined by the following formula:
((Red value X 299) + (Green value X 587) + (Blue value X 114)) / 1000
Note: This algorithm is taken from a formula for converting RGB values to
YIQ values. This brightness value gives a perceived brightness for a
color.

Color difference is determined by the following formula:
(maximum (Red value 1, Red value 2) - minimum (Red value 1, Red value 2))
+ (maximum (Green value 1, Green value 2) - minimum (Green value 1, Green
value 2)) + (maximum (Blue value 1, Blue value 2) - minimum (Blue value 1,
Blue value 2))

**
The rage (sic) for color brightness difference is 125. The range for color
difference is 500.
**
"
Techniques For Accessibility Evaluation And Repair Tools
http://www.w3.org/TR/AERT#color-contrast


And there are other color contrast analyzer algorithms which are
furthermore accessible. I read - but can not remember where - that Xerox
had color constrast algorithms furthermore accessibility-friendly.

"
about 8% of the male population have some form of color deficiency
"
Can Color-Blind Users See Your Site?
http://msdn.microsoft.com/en-us/library/Bb263953.aspx

As far as big enough font-size, humans have a 2000 years experience of
usability and printed material.

For color constrast, humans have a 50,000 - 100,000 years experience in
usability. The first drawings of deers, horses and other animals in caves
by Cro-Magnons were meeting, were most likely passing those color contrast
algorithms!

Gérard
-- 
CSS 2.1 Test suite RC6, March 23rd 2011
http://test.csswg.org/suites/css2.1/20110323/html4/toc.html

Contributions to CSS 2.1 test suite
http://www.gtalbot.org/BrowserBugsSection/css21testsuite/

Web authors' contributions to CSS 2.1 test suite
http://www.gtalbot.org/BrowserBugsSection/css21testsuite/web-authors-contributions-css21-testsuite.html
Received on Sunday, 14 October 2012 02:22:03 GMT

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