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RE: measuring contrast ratio and Windows Clear Type

From: Joe Chidzik <joe.chidzik@abilitynet.org.uk>
Date: Mon, 11 Aug 2014 05:05:10 -0500
To: Jan Eric Hellbusch <hellbusch@2bweb.de>, "w3c-wai-ig@w3.org" <w3c-wai-ig@w3.org>
Message-ID: <4602D70D47EBE642A2B85590FFB33249C5F7C6D2BC@34093-MBX-C09.mex07a.mlsrvr.com>
Whenever I've used the CCA with IE, fonts appear anti-aliased, meaning it is not clear which pixel to pick for the actual text colour. Firefox does not exhibit this problem for me, and so I've always used Firefox when measuring contrast with the CCA just to be sure I'm selecting the colours specified by the CSS. 

I don't know if it's possible to detect (via CSS\JavaScript) if a user has clear type enabled or not, but in my view, measuring the contrast via the values provided in the CSS should be all that it is required to check adherence to the success criteria.

Joe 


> -----Original Message-----
> From: Jan Eric Hellbusch [mailto:hellbusch@2bweb.de]
> Sent: 11 August 2014 10:45
> To: w3c-wai-ig@w3.org
> Subject: measuring contrast ratio and Windows Clear Type
> 
> Hi,
> 
> I was giving a seminar the other day on Web accessibility testing and was asked
> by one of the participants how I measure contrast when clear type is activated. I
> was caught by surprise, because I had switched it off when setting my Windows 7
> laptop up a couple of years ago and I never gave it a second thought. Since then I
> have been measuring contrast ratios with clear type switched off.
> 
> I have been trying to find more detailed information on the precise differences in
> measuring contrast ratios with and without clear type on Windows, but I obviously
> have the wrong search terms. Perhaps someone on this list can point me out in
> the right direction?
> 
> * Using CCA there is the possibility of grabing several pixels at a time.
> Does that solve the problem of measuring a correct contrast ratio?
> * Or do I have to switch clear type off or  (in Firefox) set gfx.content.azure.enabled
> to false?
> 
> I would greatly appreciate a hint or a resource.
> 
> Thanks,
> Jan
> 
> --
> Jan Eric Hellbusch
> Tel.: +49 (231) 33005825 oder +49 (163) 3369925
> Accessibility-Beratung: http://2bweb.de
> Blog: www.chemnitzer-14.de
> Bücher, Artikel: www.barrierefreies-webdesign.de
> 
> 
> 
Received on Monday, 11 August 2014 10:05:33 UTC

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