Create a color deficiency vision test

[andymeneely]

Given the prevalence of various forms of color-blindness and it's significant impact on gaming, I think it would be cool to have a command that shows what your cards look like to someone of various types of color blindness.

Cairo doesn't support this natively, but there are plenty of implementations out there to work from for our own implementation. Here are a few notable ones:

https://www.npmjs.com/package/color-blind
http://docs.gimp.org/en/gimp-display-filter-dialog.html#gimp-deficient-vision
http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5645874&tag=1
http://www.vischeck.com/
http://newmanservices.com/colorblind/default.asp

This is a neat overview, although light on details
http://www.ijrrr.com/papers6/paper4.pdf

The daltonize method is best laid out here:
http://link.springer.com/chapter/10.1007%2F978-3-642-23187-2_29

Assuming we can get the math right (perhaps that should become a separate gem altogether like the Node.js package), the Squib implementation would be something like:

color_deficiency range: 0,2, output: "color_deficiency.png"

The output would be a PNG showing a table of your cards along with filtered versions of the cards that simulate what the card would look like to a person with color blindness. We can also put statistics on each form of color blindness about what's more prevalent (some of the rarer forms of colorblindness are extremely hard to design with). The PNG that is automatically sized based on the card dimensions, so there's no need to size it.

[andymeneely]

http://mudcu.be/labs/Color-Vision/Javascript/Color.Vision.Simulate.js
http://www.daltonize.org/search/label/Javascript

[andymeneely]

https://github.com/emarc/Chrometric
http://colorlab.wickline.org/colorblind/colorlab/docs/legal.html
Looks like Inkscape is getting this feature too: https://bugs.launchpad.net/inkscape/+bug/790534

[andymeneely]

The filter in Inkscape is now in 0.92 under Filters > Color > Color Blindness...

Still would love to do this, although I always stop short in figuring out how to do this with cairo.