- From: Gregg Vanderheiden <gv@trace.wisc.edu>
- Date: Wed, 22 Feb 2006 01:38:23 -0600
- To: <w3c-wai-gl@w3.org>
Here are some suggested edits for the WCAG Contrast guideline Definitions 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 "luminosity contrast ratio" [old definition...] luminosity contrast ratio {{(L1+.05) / (L2+.05) where L is luminosity and is defined as .2126*R + .7152*G + .0722B using linearized R, G, and B values. Linearized R (for example) = (R/FS)^2.2 where FS is full scale value (255 for 8 bit color channels). L1 is the higher value (of text or background) and L2 is the lower value.}} [end of old definition] [new definition...] luminosity contrast ratio {{(L1 + 0.05) / (L2 + 0.05), where L1 is the luminosity of the lighter of the text and background colors, and L2 is the luminosity of the darker of the text and background colors. The luminosity of a color is defined 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. Note: Luminosity values can range from 0 (black) to 1 (white), and luminosity contrast ratios can range from 1 to 21.}} [end of new definition]
Received on Wednesday, 22 February 2006 07:38:24 UTC