Edit comment LC-1183 for Accessibility Guidelines Working Group

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Comment LC-1183: Comment Shortname:; Commenter: Greg Lowney <gcl-0039@access-research.org> on behalf of Lowney Access Research, LLC; Message-id:; Section of the document concerned:

or; Refinement of the section concerned:; Status:
assigned to; Type:; Resolution status:
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Commenter's response (URI):; Comment:
Definition of LUMINOSITY CONTRAST RATIO assumes that the foreground and background are both solid colors; it is unclear how this would be applied when that is not the case, such as when the background is a gradient or image, or when the foreground consists of many colors. A particularly interesting case is when the foreground is anti-aliased, causing different pixels to be different brightness (or, in the case of Microsoft's ClearType technology, even different colors) but all designed to be perceived as a single brightness of a single color.; Related issues: (space separated ids); WG Notes: [TEAMA] Sent note to commenter asking for suggestion. Discussed in the 15 March 2007 telecon: action: David, Michael and ben (ping Sean) to work on 1183 contrast on gradients http://www.w3.org/WAI/GL/2007/03/15-wai-wcag-minutes.html Discussed in the 03 May 2007 telecon: Accepted by unanimous consent. http://www.w3.org/WAI/GL/2007/05/03-wai-wcag-minutes.html Response: http://lists.w3.org/Archives/Public/public-comments-wcag20/2007Jun/0300.html; Resolution: Thank you, the definition of contrast has been updated to address your concerns. The new definition text is: contrast ratio (L1 + 0.05) / (L2 + 0.05), where * L1 is the relative luminance of the lighter of the foreground or background colors, and * L2 is the relative luminance of the darker of the foreground or background colors. Note 1: Contrast ratios can range from 1 to 21 (commonly written 1:1 to 21:1). Note 2: For dithered colors, use the average values of the colors that are dithered (average R, average G, and average B). Note 3: Text can be evaluated with anti-aliasing turned off. Note 4: Background color is the specified color of content over which the text is to be rendered in normal usage. If no background color is specified, then white is assumed. Note 5: For text displayed over gradients and background images, authors should ensure that sufficient contrast exists for each part of each character in the content.; (Please make sure the resolution is adapted for public consumption)