Color Blindness Simulator Now Available

Posted on June 01, 2005  |  

Posted in Design

No comments yet

When I first read about protanopia, deuteranopia, tritanopia and other vision deficiencies in Joe Clark’s Building Accessible Websites, I was all confused. I went back and re-read the section on color blindness. It surely fueled my curiosity, so I started digging deeper. This is how I came across a very interesting research, conducted by Japanese researchers, which I mentioned in my previous post.

This quest led me to VisCheck, an online color blindness simulator I’ve mentioned before as well. Since VisCheck could do it, there must’ve been a color matching algorithm to simulate at least protanopia and deuteranopia.

It seemed that all roads of computer simulation of color blindness led to these two papers:

  1. Computerized simulation of color appearance for dichromats (PDF)
  2. Digital Video Colourmaps for Checking the Legibility of Displays by Dichromats (PDF)

The second paper has both the approach and the formulas to recalculate a color as a person with “normal” vision (trichromat) would see it to that of its color blind counterpart. It was a bit weird to recall matrix and vector multiplication as I was taught back in high school.

Now that the lengthy introduction is out of the way, here’s the link to my online color blindness simulator. I’ve compared my output with that of 2-3 other simulators, and it seemed to be in line.

Please note: I have to cap uploadable image size to 500K maximum. Images larger than 500K will be rejected automatically. Also, for now I’m allowing only jpg, gif and png images. Should need arise, I’ll add other types.

Why Bother?

It took about 2 weeks to get research and code in place, in the course of which I’ve been asked more than once why I bothered. Well, I never understood color blindness before I hit a chapter on type and color in Joe Clark’s book. Also, I didn’t realize color blindness was so common.

In retrospect, I would’ve chosen the color scheme for my site a tad bit differently had I known all this a year ago. Lesson learned.

Another reason is that you see this kind of ignorance all around you. Case in point:

Sesame Street Goof-Up

The other day I was watching Sesame Street with my daughter. In one of the skits a character held up a large cookie with a red (!) letter “H” on it. The idea was to repeat the letter “H” a gazillion times so a child would remember it.

To see how this cookie with “H” on it appears to color blind people, see online article How do things look to colorblind people? See the “cookie” with “29” on it? I can kind of understand when businesses don’t give a crap (“You’re going too far”, “Nobody cares”, etc), but a kiddie show must be as accommodating as possible. Very poor show “debugging.”

Disability, Condition, Or…?

I’ve used quite a few articles and white papers while working on the simulator code. Interestingly, some authors treat color blindness almost as a terminal disease or talk condescendingly about it. Some call it “disability”, others—“problem”, “congenital or acquired impairment of color discrimination”, “disorder”. I’m no expert of accessibility all of a sudden, but I think these terms are discriminating, and I prefer the soft wording of “diminished ability to perceive differences in color.

Wikipedia has an interesting outlook on this:

Color blindness is usually labeled as a disability; however, in select situations color blind people have advantages over people with a full color range. Color blind hunters are better at picking out prey against a confusing background, and the military have found that color blind soldiers can sometimes see through camouflage that fools everyone else. Monochromats may have a minor advantage in dark vision, but only in the first five minutes of dark adaptation.