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R: WCAG Logos are not WCAG compliant?

From: Roberto Castaldo <r.castaldo@iol.it>
Date: Thu, 1 Jul 2004 14:20:04 +0200
Message-ID: <40D6B3E3003F6965@ms003msg.mail.fw> (added by postmaster@fastwebnet.it)
To: "'Doyle'" <doyleb@alaska.net>, <w3c-wai-eo@w3.org>, <w3c-wai-gl@w3.org>

Hi Doyle, Hi all,


Doyle:
I am not totally sure which of the W3C logos were tested by Andrea Martinez
(per your message above) but I looked at the following publically available
logos [1].  

Roberto:
It was exactly those logos.


Doyle:
It's my opinion as well, that no algorithm (Juicy Studio's, HP's, etc.) is
going to meet the potential need of every user.  At some point there needs
to be a set standard by which developers can determine if their background
and foreground allow a user to determine the content that is presented over
a background.

Roberto:
Agree; it's difficult, but we're trying to make testable as much SC as we
can, and this is a situation where we must give a strong signal to web
developers and web designer in particular. After all in WCAG 1.0 the
checkpoint 2.2 is already testable, as we suggest an algorithm.


Doyle:
Also, I do not believe (to the best of my knowledge) that the working group
has finalized a particular algorithm with regard to color and contrast
issues.  I know Juicy Studio was and has been looked at as a potential
option.

Roberto:
From Juicy Studio pages [1]:

"The following is the formula suggested by the World Wide Web Consortium
(W3C) to determine the brightness of a colour. 
((Red value X 299) + (Green value X 587) + (Blue value X 114)) / 1000 
The difference between the background brightness, and the foreground
brightness should be greater than 125."

And also,

"The following is the formula suggested by the W3C to determine the
difference between two colours. 
(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 difference between the background colour and the foreground colour
should be greater than 500."

From W3C WAI Techniques pages [2]:

"Color visibility can be determined according to the following algorithm:
(This is a suggested algorithm that is still open to change.)
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 for color brightness difference is 125. The range for color
difference is 500."

So, Juicy Studio adopted the same algorithm we suggest to use; I'm not
saying that it's perfect, maybe could be improved or simply change, but as
far as we suggest such an algorithm, let's respect it (in W3C web site we
should really do it).

My best regards,

Roberto Castaldo
-----------------------------------
www.Webaccessibile.Org coordinator
IWA/HWG Member
rcastaldo@webaccessibile.org
r.castaldo@iol.it
Mobile 348 3700161
Icq 178709294
----------------------------------- 


[1] http://www.juicystudio.com/services/colourcontrast.asp#brightformula
[2] http://www.w3.org/TR/AERT#color-contrast
Received on Thursday, 1 July 2004 08:21:05 UTC

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