- From: Steven Faulkner <faulkner.steve@gmail.com>
- Date: Fri, 22 Aug 2008 15:43:09 +0100
- To: "Gregg Vanderheiden" <gv@trace.wisc.edu>
- Cc: "David Woolley" <forums@david-woolley.me.uk>, "wai-ig list" <w3c-wai-ig@w3.org>
Colour Contrast Analyser Firefox Extension http://juicystudio.com/article/colour-contrast-analyser-firefox-extension.php Colour Contrast Analyser windows and MAC apps http://www.paciellogroup.com/resources/contrast-analyser.html regards stevef 2008/8/21 Gregg Vanderheiden <gv@trace.wisc.edu>: > there are contrast tools available as a plug in tool for Firefox. They may > also create one for your platform if you approach them. > I would check with faulkner.steve@gmail.com > > Gregg > ----------------------- > Gregg Vanderheiden Ph.D. > Director Trace R&D Center > Professor Ind and Biomed Engr > University of Wisconsin-Madison > > > > > > On Aug 21, 2008, at 5:11 PM, David Woolley wrote: > > Peter Thiessen wrote: > > ORCA. But as for contrast testing, an automated tool, or any sort of tool > would be helpful start. Or hell, even a few examples wouldn't hurt. > > What the formulae are doing is converting the image to greyscale and > then requiring a certain ratio between the absolute intensities of > adjacent shades of grey. The numerator and demoninator are offset > slightly so that you need a significant difference at low intensities. > > Unfortunately image manipulation tools don't seem to provide an sRGB to > linear conversion function, so you will need to perform a gamma > correction (mid level slider, or gamma function), then simply convert > the result to grayscale. (sRGB isn't a gamma curve at low intensities.) > > The one thing that this doesn't automate is looking the the contrasts in > the resulting grayscale image. To this subjectively, you should first > convert back to the colour profile of your monitor. > > The complexity in doing the greyscale conversion is in that it does it > reasonably accurately, whereas your image manipulation tool probably > goes straight into the weighted sum. > > > -- > David Woolley > Emails are not formal business letters, whatever businesses may want. > RFC1855 says there should be an address here, but, in a world of spam, > that is no longer good advice, as archive address hiding may not work. > > > > > > > > -- with regards Steve Faulkner Technical Director - TPG Europe Director - Web Accessibility Tools Consortium www.paciellogroup.com | www.wat-c.org Web Accessibility Toolbar - http://www.paciellogroup.com/resources/wat-ie-about.html
Received on Friday, 22 August 2008 14:43:44 UTC