- From: Roberto Scano - IWA/HWG <rscano@iwa-italy.org>
- Date: Mon, 9 Feb 2004 22:06:38 +0100
- To: "WCAG List" <w3c-wai-gl@w3.org>
We have discussed some weeks ago about colour contrast. I'm working with JuicyStudio for optimize the CSS testing tool [1] for test also attributes [2]. * Colour Brightness Formula The following is the formula suggested by the World Wide Web Consortium (W3C) to determine the brightness of a colour. ((Red value X 299) + (Green value X 587) + (Blue value X 114)) / 1000 The difference between the background brightness, and the foreground brightness should be greater than 125. * Colour Difference Formula The following is the formula suggested by the W3C to determine the difference between two colours. (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 difference between the background colour and the foreground colour should be greater than 500. When CSS 3 is finalised, we have some other colour values to add to the tests such as rgba, hls, hsla, opacity, and the SVG colour keywords. The algorithm provided by the W3C doesn't take into account opacity, so it may require some thinking about. Any ideas? Roberto Scano --- [1] http://www.juicystudio.com/services/csscontrast.asp [2] http://www.w3.org/TR/WCAG10-CSS-TECHS/#units
Received on Monday, 9 February 2004 16:06:57 UTC