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FW: Docs for reference to comfortable to reach - easy to read.

From: Gregg Vanderheiden <gv@trace.wisc.edu>
Date: Fri, 30 Apr 2004 10:13:07 -0500
To: <w3c-wai-gl@w3.org>
Message-ID: <auto-000022898091@spamarrest.com>
 

From materials I got from Jim Thatcher.   

 


Gregg

 -- ------------------------------ 
Gregg C Vanderheiden Ph.D. 
Professor - Ind. Engr. & BioMed Engr.
Director - Trace R & D Center 
University of Wisconsin-Madison 

  _____  

From: Jim Thatcher [mailto:jim@jimthatcher.com] 
Sent: Thursday, April 29, 2004 8:39 PM
To: 'Gregg Vanderheiden'; 'Piper, Ian'; 'Whitney Quesenbery'; 'David Aragon
(E-mail)'; 'Josephine (Josie) Scott (E-mail)'
Subject: RE: Docs for reference to comfortable to reach - easy to read.

 

Group .  Sorry, here is some grayscale rambling!

 

Here is a different grayscale test - it works well (I think).
http://colorfilter.wickline.org/. The test page is awkward - but you can
select grayscale from the combo box and paste in a url.

 

I would like a definition of grayscale. Here it is from w3.org:

An image representation in which each pixel is represented by a single
sample value representing overall luminance (on a scale from black to
white). PNG also permits an alpha sample to be stored for each pixel of a
grayscale image. 
 <http://www.w3.org/TR/PNG-Glossary.html> www.w3.org/TR/PNG-Glossary.html

So now how do you go from rgb to luminance? The first google hit on that
was:

 

There is no one "correct" conversion from RGB to grayscale, since it depends
on the sensitivity response curve of your detector to light as a function of
wavelength. A common one in use is: 

    Y = 0.3*R + 0.59*G + 0.11*B

And another:

        (red + green * 2 + blue) >> 6
(http://www.directfb.org/mailinglists/directfb-dev/2003/01-2003/msg00032.htm
l) 

 

And another: Photoshop uses a standard mix of the RGB channels for their
grayscale conversion: RED=30%, GREEN=59% and BLUE=11%.
(http://gimpguru.org/Tutorials/Color2BW/#grayscale) 

 

Looks like it's Y = 0.3*R + 0.59*G + 0.11*B 

 

Jim

Accessibility, What Not to do: http://jimthatcher.com/whatnot.htm.

Web Accessibility Tutorial: http://jimthatcher.com/webcourse1.htm.


-----Original Message-----
From: Jim Thatcher [mailto:jim@jimthatcher.com] 
Sent: Thursday, April 29, 2004 1:42 PM
To: 'Gregg Vanderheiden'; 'Piper, Ian'; 'Whitney Quesenbery'; 'David Aragon
(E-mail)'; 'John O'Hara (E-mail)'; 'Josephine (Josie) Scott (E-mail)';
'Shari Little (E-mail)'; 'Sharon Laskowski (E-mail)'; 'Ted Selker (E-mail)'
Subject: RE: Docs for reference to comfortable to reach - easy to read. 

 

http://www.q42.nl/demos/colorblindnesssimulator/

 

http://www.nils.org.au/ais/web/resources/toolbar/index.html#ins 

 

Jim

Accessibility, What Not to do: http://jimthatcher.com/whatnot.htm.

Web Accessibility Tutorial: http://jimthatcher.com/webcourse1.htm.


-----Original Message-----
From: Gregg Vanderheiden [mailto:gv@trace.wisc.edu] 
Sent: Thursday, April 29, 2004 1:13 PM
To: 'Piper, Ian'; 'Whitney Quesenbery'; 'David Aragon (E-mail)'; 'Jim
Thatcher (E-mail)'; 'John O'Hara (E-mail)'; 'Josephine (Josie) Scott
(E-mail)'; 'Shari Little (E-mail)'; 'Sharon Laskowski (E-mail)'; 'Ted Selker
(E-mail)'
Subject: Docs for reference to comfortable to reach - easy to read. 

 

 

 

 
Gregg

 -- ------------------------------ 
Gregg C Vanderheiden Ph.D. 
Professor - Ind. Engr. & BioMed Engr.
Director - Trace R & D Center 
University of Wisconsin-Madison 

 

 

 
Received on Friday, 30 April 2004 11:14:59 GMT

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