Re: Colour manipulation

[Ted Zlatanov <tzz@lifelogs.com>]

On Tue, 23 Nov 2010 16:54:34 +0100 Julien Danjou <julien@danjou.info> wrote: 

JD> On Tue, Nov 23 2010, Ted Zlatanov wrote:
>> I would recommend to let users customize a color vision profile as part
>> of color-lab (see my original long explanation of my work with colors in
>> GUI design).  Maybe just a list of colors and their contrasting pairs
>> (with a reasonable set of defaults for each of the various kinds of
>> colorblindness), from which we can approximate what will look good
>> anywhere in the colorspace, will be sufficient.  The algorithms are nice
>> to have but not essential to the original requirement.

JD> That sounds like an option indeed. I'll probably use that if I can't do
JD> something better.

JD> Now, what I have in mind…

JD> I think the only colour blindness types we should consider are all forms
JD> of dichromacy. In that case, since we use RGB (hehe), dropping one of
JD> the 3 components (depending of the dichromacy type) and using the same
JD> computing could work.

JD> If I simulate protanopia with the following code and then correct it,
JD> this is what I got:
JD>  (let* ((fg "#ffaabb")
JD>         (bg "#aaffbb")
JD>         (fg-cb (mapcar (lambda (x) (/ x 256)) (x-color-values fg)))
JD>         (bg-cb (mapcar (lambda (x) (/ x 256)) (x-color-values bg))))
JD>    (shr-color-check
JD>     ;; No red color blindness
JD>     (apply 'format "#00%02X%02X" (cdr fg-cb))
JD>     (apply 'format "#00%02X%02X" (cdr bg-cb))))

JD> ==> ("#3effce" "#0096a6")

JD> I simulate it by setting red to 0, and let the code correct the color.
JD> It generates 2 new colors: #3effce #0096a6, which are 2 different blues.
JD> Even #3effce without the red component (#00ffce) seems visible.

JD> If I use 2 different reds like #ff0000 and #bb0000 it generates black
JD> and grey: #000000 and #5e5e5e. The grey is probably viewed as #005e5e
JD> which is some green-blue, and should be visible.

JD> This is probably not perfect, but is this good enough? Any color blind
JD> people in there? :)

You can test at http://colorschemedesigner.com/

The colors you mentioned looked OK to me and yes, killing the red is
probably a good way to fix it for most people (maybe it's as simple as a
custom set of RGB adjustment constants for general use?).  You may want
to take the discussion to emacs-devel to find both more opinions and
more testers.  There may be someone that knows about existing similar
work for Emacs Lisp; I already searched but didn't find any.

Ted