Colour contrast analyser (Full Version)

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womble -> Colour contrast analyser (3/19/2007 19:07:19)

quote:

...a tool for checking foreground & background colour combinations to determine if they provide good colour visibility. Determining "colour visibility" is based on algorithms suggested by the World Wide Web Consortium (W3C)


quote:

The Colour Contrast Analyser (CCA) is useful to help determine, in particular, the legibility of text on a web page and the legibility of image based representations of text.

Assessing conformance with Checkpoint 2.2 of the Web Content Accessibility Guidelines 1.0

Checkpoint 2.2 of the WCAG 1.0 requires that "foreground and background colour combinations provide sufficient contrast when viewed by someone having colour deficits, or when viewed on a black and white screen."

Use the CCA to test colour combinations against the W3C's suggested algorithm for determining "sufficient contrast".


http://www.nils.org.au/info.aspx?page=628

A nice little app. Enter either the hex number of the background and foreground colours, or use the dropper tool to select the colours, and get a result for both normal vision and different types of colour blindness, as well as seeing a simulation of an area of the screen for different types of colour blindness, and also see what you page might look like to someone with cataracts.




mtfm -> RE: Colour contrast analyser (3/20/2007 15:40:29)

Looks cool, from what I can see. Might see if I can find someone round here who will let me try it on their computer.

Kind of ironic, though because this particular item is not available on Mac and therefore not accessible to yours truly.

(I have a Mac at home, and here at work I know better than to even ask about downloading freeware anything.)



d a v e -> RE: Colour contrast analyser (3/20/2007 16:11:24)

does the firefox extensions work for mac??



womble -> RE: Colour contrast analyser (3/20/2007 16:12:09)

Ah, so you work for one of those employers as well!

<off-topic>Today I had to write a report to the corporate IT committee outlining why I wanted to buy and install a £40 app to help me run my library at work. It's cost more in my time to write the damn report than to buy the app [:@]</off-topic>

Hmmmm, I'd not noticed it was PC only....



jaybee -> RE: Colour contrast analyser (3/20/2007 17:44:52)

I use those but the new checkers use the WCAG rules which include luminosity and one site which passes the contrast and brilliance checks, fails luminosity. I'm coming to the conclusion that unless you use black on white you'll never win.

Try it, Juicy Studio have a colour checker and a luminosity checker.



Donkey -> RE: Colour contrast analyser (3/20/2007 19:31:17)

I think the loonies have taken over the asylum. Not much of this makes sense to me.

If your site passes on the various criteria for colourblind people (simply put if it's legible when viewed in grayscale) that's all that matters. Any non-colourblind person who may have a problem distinguishing between background and foreground colours that look OK in grayscale should be using a screenreader.

This colour facisim is wrong headed and should be rethought before it becomes accepted wisdom and nobody dares to challenge it.

I'm thinking of launching a site where you can see what your page looks like to someone who has their eyes shut. It makes just as much sense.



jaybee -> RE: Colour contrast analyser (3/20/2007 19:56:17)

I have to admit the luminosity thing leaves me confused. For example a white background with red text, #fff and #f00 the checkers say it's OK but it fails luminosity. Go figure.



rubyaim -> RE: Colour contrast analyser (3/20/2007 20:57:41)

Out of idle curiosity I just did a search for luminosity and am really none the wiser.

http://www.w3.org/TR/WCAG20/appendixA.html
quote:


luminosity contrast ratio

(L1 + 0.05) / (L2 + 0.05), where L1 is the luminosity of the lighter of the text or background colors, and L2 is the luminosity of the darker of the text or background colors.

Note 1: The luminosity of a color is defined as 0.2126 * ((R / FS) ^ 2.2) + 0.7152 * ((G / FS) ^ 2.2) + 0.0722 * ((B / FS) ^ 2.2).

*

R, G, and B are the red, green, and blue RGB values of the color.
*

FS is the maximum possible full scale RGB value for R, G, and B (255 for eight bit color channels).
*

The "^" character is the exponentiation operator.

Note 2: Luminosity values can range from 0 (black) to 1 (white), and luminosity contrast ratios can range from 1 to 21.


The thing at Jucy Studio about Luminosity Contrast Ratio Algorithm was a bit better.

I think I'll just continue to rely on common sense [:o]

Jaybee, maybe #fff and #f00 share too many f's when divided by #ddd, multiplied by 1258.3333345, and then subtracted from 2 [:D]



Tailslide -> RE: Colour contrast analyser (3/21/2007 2:30:31)


quote:

ORIGINAL: rubyaim
The thing at Jucy Studio about Luminosity Contrast Ratio Algorithm was a bit better.



Or as it was described to me recently by some rather well known in the area of accessibility:

quote:

Gez Lemon's Little Tool



Donkey -> RE: Colour contrast analyser (3/21/2007 5:30:23)

quote:


quote:

Gez Lemon's Little Tool

Perhaps someone should forward him a few of those medical enhancement emails we all keep getting. [;)]



jaybee -> RE: Colour contrast analyser (3/21/2007 6:57:28)

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Gez Lemon's Little Tool
That could be taken completely the wrong way, as evidenced by the above post. [:D]

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Or as it was described to me recently by some rather well known in the area of accessibility:
Wouldn't be a certain person by the name of PL would it.



jaybee -> RE: Colour contrast analyser (3/21/2007 7:37:00)

Aaaaaargh!

This is where I shout "UNCLE"



Tailslide -> RE: Colour contrast analyser (3/21/2007 9:54:12)


quote:

ORIGINAL: jaybee

quote:

Gez Lemon's Little Tool
That could be taken completely the wrong way, as evidenced by the above post. [:D]

quote:

Or as it was described to me recently by some rather well known in the area of accessibility:
Wouldn't be a certain person by the name of PL would it.


It would.

I take these contrast tools as a starting point - they're useful but as Mel/Rich's article state, increased font size / emboldening will reduce the issue as long as there's not too much of a lack of contrast to start with.

For instance, I generally use #555 for body text instead of #666 which is what I started out using - it passed the "lemon" test and makes no real difference to me. But I have used colours that technically have failed that test - although at a larger font size for headings etc.




jaybee -> RE: Colour contrast analyser (3/21/2007 10:17:38)

Somebody needs to jump on these WCAG2 recommendations fast before we all get saddled with them.



womble -> RE: Colour contrast analyser (3/21/2007 10:41:29)


quote:

ORIGINAL: Donkey
If your site passes on the various criteria for colourblind people (simply put if it's legible when viewed in grayscale) that's all that matters. Any non-colourblind person who may have a problem distinguishing between background and foreground colours that look OK in grayscale should be using a screenreader.

This colour facisim is wrong headed and should be rethought before it becomes accepted wisdom and nobody dares to challenge it.


quote:

Any non-colourblind person who may have a problem distinguishing between background and foreground colours that look OK in grayscale should be using a screenreader.


Not true.

As some of you know, I have some visual problems due to a neurological condition, problems which have recently been getting worse, and thus spent this morning online window shopping for screen magnification software, and I discovered the number of sites selling assistive technologies who have serious accessibility problems in some areas is rather alarmingly high. That's a different story though.

Apart from having very variable visual accuity, I also have double vision, which isn't fully corrected by all the prisms my specs are loaded up with. Result? Sometimes, not bad, other times fuzzy and quite a few echoes of the same image overlapping. Even something that's fairly okay in greyscale, when made fuzzy and multiplied, loses it's clarity, so the contrast has to be very strong. Depending on which computer I'm on I can vary the resolution - at work I have particular problems so that's on 800x600 on a 21" monitor at the moment. On a bad day if I'm in the office I'll do stuff that doesn't need the computer, and if it's a 'web' day, the computer unfortunately stays off.

I certainly don't think I'm quite ready for a screenreader just yet though.

Luminosity's also important for a variety of reasons, including incidently sometimes for people with normal vision. I run a forum for people with the same condition I have, and when we recently moved sites and I installed different forum software there were howls of protest at the colour scheme and even one of my admins walked out and refused to come back until I installed a different theme. Why? There was plenty of contrast - because the background was white - #fff. That was a problem because a lot of the forum members suffer from photophobia - a sensitivity to light. Bright white backgrounds have too much 'glare'. Other conditions produce different problems - a friend of mine has Usher Syndrome. As well as having tunnel vision, she has photophobia, and Retinitis pigmentosa so she also has problems with particular colour schemes because she finds it difficult to identify colours (not the same as colour-blindness). A screen reader wouldn't be much use to her because she's also profoundly deaf.



jaybee -> RE: Colour contrast analyser (3/22/2007 5:45:58)

The problems here are that WCAG are insisting on certain levels. Those levels in some cases are too bright and as Womble says can cause problems for others. It's been found that high lumen makes the pages hard to read for dyslexics, a far larger sector of the population (est. 1 in 10) than blind or visually impaired.

Now I'm happy to provide different stylesheets for different visitors but I object to having my pages chucked out of the validators because they don't use a scheme that is inherently unusable, either for dyslexics, V.I. or normal sighted people who get raging headaches looking at the page.

I can understand the validators flagging this as a warning for manual checks, I could even understand them suggesting schemes but outright invalidating your page based on WCAG values that clearly have not been thought through properly is just not on.



womble -> RE: Colour contrast analyser (3/22/2007 7:47:09)


quote:

ORIGINAL: jaybee

Now I'm happy to provide different stylesheets for different visitors but I object to having my pages chucked out of the validators because they don't use a scheme that is inherently unusable, either for dyslexics, V.I. or normal sighted people who get raging headaches looking at the page.

I can understand the validators flagging this as a warning for manual checks, I could even understand them suggesting schemes but outright invalidating your page based on WCAG values that clearly have not been thought through properly is just not on.


That's the problem. There isn't a one size fits all solution that suits everyone, which I think is what the WCAG is trying to do.

Btw, at the moment I'm trying out a demo version of LunarPlus in a "try before you buy" kind of way. It has basic output to speech (nothing like what the likes of Jaws etc. can do) and screen magnification, which is very handy but takes a bit of getting used to. The best bit I discovered last night though - it has built-in colour changing styles that affect not only web pages but all apps - meaning that the glare problem is gone instantly. Some of the styles though sure mess up pretty websites. Pleased to report though that although OF looks a little weird with a blue tinge to it, it's still pretty usable. [;)]



jaybee -> RE: Colour contrast analyser (3/22/2007 9:23:59)

Any idea if that runs alongside Jaws?



womble -> RE: Colour contrast analyser (3/22/2007 16:06:06)

Um, not sure. I read elsewhere what you said about Jaws messing with drivers and stuff so I didn't feel inclined to download a trial of that. [:D] I know LunarPlus connected to the internet when I switched on to update some map files or something, so it obviously does something with files - at least the installed version does. I'd imagine the pen version should be pretty safe as it runs from a USB drive without installing anything to the machine.



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