gistfile1.txt

require 'rmagick'

colors = ["#660000", "#990000", "#cc0000", "#cc3333", "#ea4c88",
   "#993399", "#663399", "#333399", "#0066cc", "#0099cc", "#66cccc",
   "#77cc33", "#669900", "#336600", "#666600", "#999900", "#cccc33",
   "#ffff00", "#ffcc33", "#ff9900", "#ff6600", "#cc6633", "#996633",
   "#663300", "#000000", "#999999", "#cccccc", "#ffffff"];

def convert_rgb_to_xyz(r, g, b)
   var_R = ( r / 255.0 )                     # RGB from 0 to 255
   var_G = ( g / 255.0 )
   var_B = ( b / 255.0 )

   if ( var_R > 0.04045 )
      var_R = ( ( var_R + 0.055 ) / 1.055 ) ** 2.4
   else
      var_R = var_R / 12.92
   end

   if ( var_G > 0.04045 )
      var_G = ( ( var_G + 0.055 ) / 1.055 ) ** 2.4
   else
      var_G = var_G / 12.92
   end

   if ( var_B > 0.04045 )
      var_B = ( ( var_B + 0.055 ) / 1.055 ) ** 2.4
   else
      var_B = var_B / 12.92
   end

   var_R = var_R * 100
   var_G = var_G * 100
   var_B = var_B * 100

   # Observer. = 2°, Illuminant = D65
   x = var_R * 0.4124 + var_G * 0.3576 + var_B * 0.1805
   y = var_R * 0.2126 + var_G * 0.7152 + var_B * 0.0722
   z = var_R * 0.0193 + var_G * 0.1192 + var_B * 0.9505

   return { :x => x, :y => y, :z => z }
end

def convert_xyz_to_lab(x, y, z)
   # Observer= 2°, Illuminant= D65
   var_X = x / 95.047
   var_Y = y / 100.000
   var_Z = z / 108.883

   if ( var_X > 0.008856 )
      var_X = var_X ** ( 1.0/3.0 )
   else
      var_X = ( 7.787 * var_X ) + ( 16.0 / 116.0 )
   end


   if ( var_Y > 0.008856 )
      var_Y = var_Y ** ( 1.0/3.0 )
   else
      var_Y = ( 7.787 * var_Y ) + ( 16.0 / 116.0 )
   end

   if ( var_Z > 0.008856 )
      var_Z = var_Z ** ( 1.0/3.0 )
   else
      var_Z = ( 7.787 * var_Z ) + ( 16.0 / 116.0 )
   end

   l = ( 116 * var_Y ) - 16
   a = 500 * ( var_X - var_Y )
   b = 200 * ( var_Y - var_Z )

   return { :l => l, :a => a, :b => b }
end

colors_lab = []

colors.each do |color|
   color_rgb = Magick::Pixel.from_color(color)
   r = color_rgb.red / 256
   g = color_rgb.green / 256
   b = color_rgb.blue / 256
   xyz = convert_rgb_to_xyz(r,g,b)
   lab = convert_xyz_to_lab(xyz[:x],xyz[:y],xyz[:z])
   array = [color, lab]
   colors_lab << array
end

r = 52
g = 104
b = 154

color_rgb = Magick::Pixel.from_color("#1FA5D2")
r = color_rgb.red / 256
g = color_rgb.green / 256
b = color_rgb.blue / 256
xyz = convert_rgb_to_xyz(r,g,b)
lab = convert_xyz_to_lab(xyz[:x],xyz[:y],xyz[:z])

distances = []

colors_lab.each do |color|
   l1 = lab[:l]
   a1 = lab[:a]
   b1 = lab[:b]
   l2 = color[1][:l]
   a2 = color[1][:a]
   b2 = color[1][:b]

   distance = ( ((l2 - l1)**2) + ((a2 - a1)**2) + ((b2 - b1)**2) )

   array = [color[0], distance]
   distances << array
end

p distances