Algorithm to simulate color blindness?

Question

There are many tools online that take images and simulate what that image might look like to someone with color blindness. However, I can't find any descriptions of these algorithms.

Is there a standard algorithm used to simulate color blindness? I'm aware that there are many types of color blindness (see the Wikipedia page on the subject for more details), but I'm primarily interested in algorithms for simulating dichromacy.

Answer 1

I had the same frustration and wrote an article comparing opensource color blindness simulations. In short, there are four main algorithms:

1. Coblis and the "HCIRN Color Blind Simulation function". You'll find this one in many places, and a Javascript implementation by MaPePeR. The full HCIRN simulation function was not properly evaluated but is reasonable in practice. However the "ColorMatrix" approximation by colorjack is very inaccurate and should be totally avoided (the author himself said that). Unfortunately it's still widespread as it was easy to copy/paste.

2. "Computerized simulation of color appearance for dichromats" by Brettel, Viénot, and Mollon (1997). A very solid reference. Works for all kinds of dichromacies. I wrote a public domain C implementation in libDaltonLens.

3. "Digital video colourmaps for checking the legibility of displays by dichromats" by Viénot, Brettel and Mollon (1999). A solid reference too, simplifies the 1997 paper for protanopia and deuteranopia (2 of the 3 kinds of color blindness). Also in libDaltonLens.

4. "A Physiologically-based Model for Simulation of Color Vision Deficiency" by Machado et al. (2009). Precomputed matrices are available on their website, which makes it easy to implement yourself. You just need to add the conversion from sRGB to linearRGB.