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RE: TR Checkpoint 1.4

From: Gregg Vanderheiden <gv@trace.wisc.edu>
Date: Thu, 30 Jan 2003 17:20:24 -0600
To: w3c-wai-gl@w3.org
Message-id: <00ac01c2c8b6$2be18c00$ac17a8c0@TOSHIBATABLET>

The following proposal is quite interesting.

Does anyone know:

1) if this really yields accessible text?

2) if it is all required?
	- for example, why does the color have to be different if the
brightness is different?    Aren't  very dark grey and white are the same
color?   Why would dark navy letters on sky blue (of the same hue) not be
acceptable?

3) whether it is easy to measure these things.

Otherwise very interesting...  



Andi Snow Weaver wrote:


Proposal # 4B:
- text content is not presented over a background image or color OR the
colors used for the text and background or background image pass the
following test (from Techniques For Accessibility Evaluation And Repair
Tools, dated April 26, 2000):
   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 range for color brightness difference is 125. The range for color
   difference is 500.




 
Gregg

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


-----Original Message-----
From: w3c-wai-gl-request@w3.org [mailto:w3c-wai-gl-request@w3.org] On Behalf
Of Andi Snow-Weaver
Sent: Wednesday, January 29, 2003 4:39 PM
To: w3c-wai-gl@w3.org
Subject: TR Checkpoint 1.4






Comment # 1
Minimum success criteria contains the phrases "seriously interfere" and
"easily removed" which are too subjective
WWAAC (via David Poulson and Colette Nicolle), 4 Nov 2002
<http://lists.w3.org/Archives/Public/w3c-wai-gl/2002OctDec/0135.html>
Mark Schult, 21 Oct 2002
<http://lists.w3.org/Archives/Public/w3c-wai-gl/2002OctDec/0075.html>
IBM  (via Andi Snow-Weaver), 29 Oct 2002
<http://lists.w3.org/Archives/Public/w3c-wai-gl/2002OctDec/0117.html>

Proposal # 1:
Minimum success criteria:
- text content which is presented over a background image or color is
implemented using mechanisms that allow the user to remove the background
image or color.
- no audio criteria at this level.
<Comment: the propsal for no minimum success criteria for audio derives
from followup discussions between Andi and Gregg. Gregg asserts that there
is no need for a  parallel audio success criteria here because there is
already a requirement to provide captions or transcripts for audio content.
If the background sounds are interfering, the user can read the captions or
the transcript.>

Comment # 2
WWAAC (via David Poulson and Colette Nicolle), 4 Nov 2002
<http://lists.w3.org/Archives/Public/w3c-wai-gl/2002OctDec/0135.html>
Example 2: Missing value- assumed to be 20db for consistency.

Proposal # 2:
Modify the example to match the success criteria. If the value in the
success criteria changes, update the example to match the new value.

Comment # 3
IBM (via Andi Snow-Weaver), 29 Oct 2002
<http://lists.w3.org/Archives/Public/w3c-wai-gl/2002OctDec/0117.html>
Level 2 success criteria
this success criteria should be moved to level 3 and modified as follows:
A simulator for "major types of color blindness" is a testing tool, not a
success criteria. The guidelines should specify the exact criteria to be
met similar to the one defined in level 3 for background sounds in audio
content.. A simulator may exist or may be developed that automates the
process of evaluating against the success criteria but but the tool itself
should not be the success criteria.

Proposal # 3:
Move to Level 3 success criteria and reword as follows:
- when text content is presented over a background image or color, the text
is easily readable when the page is viewed in black and white.

Comment # 4
IBM (via Andi Snow-Weaver), 29 Oct 2002
<http://lists.w3.org/Archives/Public/w3c-wai-gl/2002OctDec/0117.html>
Level 3 success criteria
the criteria at this level should result in a choice of either you don't
have background images/audio or your images/audio meet criteria that are
not a problem (pass color blind criteria, background sounds at least 20 db
lower than foreground content, etc.)
for the audio criteria, is there a time consideration here? For example, if
the background sound is not 20 db lower than the foreground content but it
only lasts for a second, is that a problem?

Proposal # 4A:
- text content is not presented over a background image or color OR the
text is easily readable when the page is viewed in black and white.
- audio content does not contain background sounds OR the background sounds
are at least ?? db lower than the foreground audio content.

Proposal # 4B:
- text content is not presented over a background image or color OR the
colors used for the text and background or background image pass the
following test (from Techniques For Accessibility Evaluation And Repair
Tools, dated April 26, 2000):
   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 range for color brightness difference is 125. The range for color
   difference is 500.
- audio content does not contain background sounds OR the background sounds
are at least ?? db lower than the foreground audio content.

Comment # 5
SAP (via Audrey Weinland), 31 Oct 2002
<http://lists.w3.org/Archives/Public/w3c-wai-gl/2002OctDec/0130.html>
minimum level #2: "prepared audio presentations" What does "prepared" mean?
Not real-time? How does/do personalization/user settings affect this? If
you provide personalization, do you meet the requirement, or does the
default setting in the Web app have to comply?

Proposal # 5:
When we use the phrase "prepared audio presentation" to mean that which is
not real time, we are getting into "policy" issues.
In the above proposals, the only audio success criteria has been moved to
Level 3. Thus for level 1 compliance, this checkpoint would not be
applicable to audio content. Under checkpoint 1.1, the audio content must
have captions or an equivalent transcript.

Comment # 6
SAP (via Audrey Weinland), 31 Oct 2002
<http://lists.w3.org/Archives/Public/w3c-wai-gl/2002OctDec/0130.html>
level 2 #1: "have been run through a simulator" Which simulator, and how do
we use it? We've used one before, and it did not recognize the SAP color
palette. It would take a lot of work to pre-screen for potential "problem
screens." This should be a Level 3 criterion unless sample testing is
enough, because otherwise it is a very tall order for a Web app.

Proposal # 6:
 Above proposal already recommends moving this requirement to level 3 and
rewording as follows:
- text content is not presented over a background image or color OR the
text is easily readable when the page is viewed in black and white.

Andi
andisnow@us.ibm.com
IBM Accessibility Center
(512) 838-9903, http://www.ibm.com/able
Internal Tie Line 678-9903, http://w3.austin.ibm.com/~snsinfo
Received on Thursday, 30 January 2003 18:21:06 GMT

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