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Colour contrast
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| amdunn | Subject: Colour contrast |  |
| I have found some discrepancies between the checker output and other tests I have applied (specifically the Minimum Contrast test, WCAG 2.0 level AA, check 301) and when I use several other colour contrast calculators, I get PASS results for a couple of colour combinations that AChecker reports as FAIL. For instance, I have tested a page with WHITE (FFFFFF) text on BROWN (7A451C) background -- this reports a FAIL on AChecker but various contrast testers report a PASS (for instance, try this colour combination on webaim.org/resources/contrastchecker/ or on snook.ca/technical/colour_contrast/colour.html which reports a brightness difference of 174, a colour difference of 546, and a contrast ratio of 7.79 -- all compliant at level AA. Another example: BLACK (000000) text on YELLOW (FFFF00) background -- snook.ca reports brightness difference of 225, colour difference of 510 and contrast ratio of 19.5 -- again, fully compliant. Yet this combination fails on AChecker. Posted: 2011-12-09 13:16:05 | ||
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greg | Subject: Re: Colour contrast | |
| Are you able to share the location of the page in which these colours used? Posted: 2011-12-09 13:34:11 | ||
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| amdunn | Subject: Re: Colour contrast | |
| One example is the page bolton.scoutgroup.ca that definitely indicates problems with the contrast ratios of the colours on the left-hand side navigation links (coloured area). Posted: 2011-12-09 13:41:54 | ||
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| greg | Subject: Re: Colour contrast | |
| Looks like you found a bug. The function that detects colors turns out to be case sensitive. If you were to change things to all lower case, it will pass. bug reported at: atutor.ca/atutor/mantis/view.php?id=4937 That said, you should also run the HTML validator on your page. It would detect the uppercase words, which are not valid when using xhtml. Posted: 2011-12-09 14:56:07 | ||
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| amdunn | Subject: Re: Colour contrast | |
| The intent was not to use XHTML. I only did that while playing with various options at setting LANG values to conform to the language requirement. I've stripped it back to HTML 4 (in which the uppercase words should be legal) and I've verified it against the HTML validator, which reports 0 errors, and confirmed that the issue with colour contrast validation still exists. Posted: 2011-12-09 15:31:13 | ||
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| greg | Subject: Re: Colour contrast | |
| That's correct. AChecker fails on the uppercase words. Maybe I wasn't clear enough. Changing the HTML version would not fix the problem in AChecker. Now-a-days Web authors do not use capitalized attributes and values in their HTML. AChecker should still be able to handle that, and we will fix the problem in the next development cycle, but you might want to get into the habit of writing all your markup in lowercase. For now if you want it to pass AChecker, change your uppercase to lowercase fonts. Posted: 2011-12-09 15:40:07 | ||
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| amdunn | Subject: Re: Colour contrast | |
| I agree with you... but the change was to be able to say it is a "conforming" HTML page (which it is -- I agree that it was non-conforming as XHTML) and yet I am aware that AChecker will mis-parse it. That being said, most of the markup is dynamically generated and it's a non-trivial change to rewrite all the code libraries that generate markup as output to flip everything to lower case... Most newer code does, in fact, write lower case markup, but this is one that doesn't (but as conforming HTML, I agree that AChecker should handle the uppercase correctly, and I understand that it will do so in the future). Thanks for your time! Posted: 2011-12-09 15:49:59 | ||
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