- From: Gregg Vanderheiden <gv@trace.wisc.edu>
- Date: Wed, 22 Feb 2006 01:43:30 -0600
- To: <w3c-wai-gl@w3.org>
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 UTC