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2.3 Suggested edits for guidelines 2.3 on Seizure disorders

From: Gregg Vanderheiden <gv@trace.wisc.edu>
Date: Wed, 22 Feb 2006 01:43:30 -0600
To: <w3c-wai-gl@w3.org>
Message-ID: <002301c63783$ae934b90$ee8cfea9@NC6000BAK>


Here are some suggested edits for the WCAG Photosensitive Epilepsy guideline
Definition.  

They are to clarify some ambiguous parts but do not change the guidelines.


Gregg

 -- ------------------------------ 
Gregg C Vanderheiden Ph.D. 
Professor - Ind. Engr. & BioMed Engr.
Director - Trace R & D Center 
University of Wisconsin-Madison 
The Player for my DSS sound file is at http://tinyurl.com/dho6b 


Note:  All modified content segments are enclosed in double braces {{}}




definition for "general flash threshold"


[old definition...]

general flash threshold 
A sequence of flashes or rapidly changing image sequences where both the
following occur:

1.  the combined area of flashes occurring concurrently (but not necessarily
contiguously) occupies more than one quarter of any {{335 x 268}} pixel
rectangle anywhere on the displayed screen area when the content is viewed
at 1024 by 768 pixels and

2.  there are more than three flashes within any one-second period.

Note: For the general flash threshold, a flash is defined as a pair of
opposing changes in brightness of 10% or more of full scale white
brightness, where brightness is calculated as {{.2126*R + .7152*G + .0722B
using linearized R, G, and B values. Linearized-X = (X/FS)^2.2 where FS is
full scale (usually 255 today)}}. An "opposing change" is an increase
followed by a decrease, or a decrease followed by an increase.

[end of old definition]


[new definition...]

general flash threshold 
sequence of flashes or rapidly changing image sequences where both the
following occur:

1.  the combined area of flashes occurring concurrently (but not necessarily
contiguously) occupies more than one quarter of any {{341 x 256}} pixel
rectangle anywhere on the displayed screen area when the content is viewed
at 1024 by 768 pixels and

2.  there are more than three flashes within any one-second period.

Note: For the general flash threshold, a flash is defined as a pair of
opposing changes in brightness of 10% or more of full scale white
brightness, where brightness is calculated as {{0.2126 * ((R / FS) ^ 2.2) +
0.7152 * ((G / FS) ^ 2.2) + 0.0722 * ((B / FS) ^ 2.2). R, G, and B are the
red, green, and blue RGB values of the color; FS is the maximum possible
full scale RGB value for R, G, and B (255 for eight bit color channels); and
the "^" character is the exponentiation operator}}. An "opposing change" is
an increase followed by a decrease, or a decrease followed by an increase.

[end of new definition]


############################################################
definition for "red flash threshold"
also present in body of "How to Meet Success Criterion 2.3.2{{1}}"


[old definition...]

red flash threshold 
A transition to or from a saturated red where both of the following occur:

1.  the combined area of flashes occurring concurrently occupies more than
one quarter of any {{335 x 268}} pixel rectangle anywhere on the displayed
screen area when the content is viewed at 1024 by 768 pixels and

2.  there are more than three flashes within any one-second period.

[end of old definition]


[new definition...]

red flash threshold 
A transition to or from a saturated red where both of the following occur:

1.  the combined area of flashes occurring concurrently occupies more than
one quarter of {{341 x 256}} pixel rectangle anywhere on the displayed
screen area when the content is viewed at 1024 by 768 pixels and

2.  there are more than three flashes within any one-second period.

[end of new definition]
Received on Wednesday, 22 February 2006 07:43:54 GMT

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