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Re: 2.3 cleanup- URL reference?

From: Sailesh Panchang <sailesh.panchang@deque.com>
Date: Tue, 24 Feb 2004 11:01:48 -0500
Message-ID: <01cc01c3faef$82e2df60$a201a8c0@deque.local>
To: "Gregg Vanderheiden" <po@trace.wisc.edu>, <w3c-wai-gl@w3.org>
I was trying to check out the Wisconsin Computer Equivalence Algorithm link given in this mail. It gives a page not found error. The searchh on the wisc.trace.edu site too was not fruitful. Will appreciate  if you can  correct the link address.
Thanks,
Sailesh
----- Original Message ----- 
  From: Gregg Vanderheiden 
  To: w3c-wai-gl@w3.org 
  Sent: Tuesday, February 24, 2004 1:19 AM
  Subject: FW: 2.3 cleanup


  Here is a cleaned up version of the new 2.3 proposal based on discussion on the list and telecom.



  Gregg







  Guideline 2.3 Allow users to avoid content that could cause photosensitive epileptic seizures.
  Level 1 Success Criteria for Guideline 2.3
    1.. Content that violates the General Flash Threshold or Red Flash Threshold  is marked in way that the user can access prior to its appearance. [I] 
  Level 2 Success Criteria for Guideline 2.3 
    1.. Content does not violate the General Flash Threshold or Red Flash Threshold. [V] 
  Level 3 Success Criteria for Guideline 2.3 
    1.. Content does not violate any Spatial Pattern Thresholds. [V] 




  General Flash Threshold 

      a.. A sequence of flashes or rapidly changing image sequences is not permitted when both the following occur: 
        1.. the combined area of flashes occurring concurrently (but not necessarily contiguously) occupies more than one quarter of any 355 x 268 pixel rectangle anywhere on the displayed screen area when the page is viewed at 1024 by 768 pixels and 
        2.. there are more than three flashes within any one-second period. 
  For this general flash threshold - a flash is defined as a pair of opposing changes in luminance (i.e., an increase in luminance followed by a decrease, or a decrease followed by an increase) of 20 candelas per rectangle meter (cd.m-2) or more and where the screen luminance of the darker image is below 160 cd.m-2. 

  Red Flash Threshold 

      a.. A transition to or from a saturated red at any luminance level is not permitted when both of the following occur: 
        1.. the combined area of flashes occurring concurrently occupies more than one quarter of any 355 x 268 pixel rectangle anywhere on the displayed screen area when the page is viewed at 1024 by 768 pixels and 
        2.. there are more than three flashes within any one-second period. 
  For the red flash threshold - a flash is defined as any pair of opposing transitions to or from a saturated red at any luminance level . (See notes 1 and 2) 

  Spatial Pattern Thresholds 

      a.. Clearly discernible stripes consisting of more than five light-dark pairs in any orientation are not permitted when the stripes are stationary when the pattern occupies more than 40% of any 355 x 268 pixel rectangle anywhere on the displayed screen area when the page is viewed at 1024 by 768 pixels. 
      b.. Clearly discernible stripes consisting of more than five light-dark pairs in any orientation that change direction, oscillate, flash, or reverse in contrast are not permitted when the pattern occupies more than 25% of any 355 x 268 pixel rectangle anywhere on the displayed screen area when the page is viewed at 1024 by 768 pixels. 
  Clearly discernable stripes are stripes where the screen luminance of the darker bars in the pattern is below 160 cd.m-2 and differs from the lighter bars by 20 cd.m-2 or more

  Note: 

  1.      Video waveform luminance is not a direct measure of display screen brightness. Not all display devices have the same gamma characteristic, but a display with a gamma of 2.2 may be assumed for the purpose of determining electrical measurements made to check compliance with these guidelines.

  2.      For the purpose of measurements made to check compliance with these guidelines, pictures are assumed to be displayed with peak white corresponds to a screen illumination of 200 cd.m-2. 

  3.      Thresholds are based on ITC Guidance Note for Licensees on Flashing Images and Regular Patterns in Television (Revised and re-issued July 2001) (http://www.ofcom.org.uk/codes_guidelines/broadcasting/tv/vrs_code_notes/flsh_imgs/?a=87101) 
  as modified by the Wisconsin Computer Equivalence Algorithm.

  Editorial Note: A free tool will be available from the University of Wisconsin's Trace Center that will carry out the above analysis on Web content.   The tool will be available by the second quarter of 2004. 







  Definitions: 


  Wisconsin Computer Equivalence Algorithm 

  The Wisconsin Computer Equivalence Algorithm is a method for applying the United Kingdom's ITC "ITC Guidance Note for Licensees on Flashing Images and Regular Patterns in Television (Revised and re-issued July 2001)" to content displayed on a computer screen, such as web pages and other computer content. The ITC Guidance Document is based on the assumption that the television screen occupies the central ten degrees of vision. This is not accurate for a screen which is located in front of a person. The Wisconsin Algorithm basically carries out the same analysis as the ITC Guidelines except that is does it on every possible ten degree window for a prototypical computer display. For complete details see http://__________.

  Editorial Note:   Appropriate link to referen         ces will be provided when they become available

  marked in way that the user can access prior to its appearance 

              

  The content is marked in a fashion that would allow the user to determine that provocative material is coming so that the user may avoid it.   Some methods that might be used for this include:

           metadata on page

           information in header (so search engine shows it)

           notification on page before provocative information is encountered.

  Editorial Note: This definition needs work.
Received on Tuesday, 24 February 2004 10:51:32 UTC

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