Simulate Deuteranope vision in ruby-vips.

daltonize.rb

#!/usr/bin/ruby

require 'rubygems'
require 'vips'

a = VIPS::Image.jpeg(ARGV[0], :sequential => true)

# import to CIELAB colour space using the ICC profile embedded in the image
lab = a.icc_import_embedded(:relative)

# turn to XYZ, a linear light space
xyz = lab.lab_to_xyz()

# and now to bradford cone space (a variant of LMS)
brad = xyz.recomb([[0.8951,  0.2664, -0.1614],
                   [-0.7502,  1.7135,  0.0367],
                   [0.0389, -0.0685,  1.0296]])

# through the Deuteranope matrix, see
# http://moinmo.in/AccessibleMoin?action=AttachFile&do=view&target=daltonize.py
deut = brad.recomb([[1, 0, 0],
                    [0.494207, 0, 1.24827],
                    [0, 0, 1]])

# back to xyz (this is the inverse of the brad matrix above)
xyz = deut.recomb([[0.987, -0.147, 0.16],
                   [0.432, 0.5184, 0.0493],
                   [-0.0085, 0.04, 0.968]])

# .. and export to sRGB for saving
rgb = xyz.xyz_to_srgb()

rgb.write(ARGV[1])