Sorted colours

sorted_colors.rb

ruby -r chunky_png -r base64 -e '
   side   = 20
   colors = {#  RR    GG    BB    AA
     red:    [0xFF, 0x00, 0x00, 0xFF],
     orange: [0xFF, 0x7F, 0x00, 0xFF],
     yellow: [0xFF, 0xFF, 0x00, 0xFF],
     green:  [0x00, 0xFF, 0x00, 0xFF],
     blue:   [0x00, 0x00, 0xFF, 0xFF],
     indigo: [0x4B, 0x00, 0x82, 0xFF],
     violet: [0x94, 0x00, 0xD3, 0xFF],
   }

   sorts = {
     hex: proc do |name, rgba|
       rgba
     end,
     roygbiv: proc do |name, (r, g, b, a)|
       min, _, max = [r,g,b].sort
       case ∆ = (max - min).to_f
       when 0 then 0
       when r then (g-b)/∆%6
       when g then (b-r)/∆+2
       else        (r-g)/∆+4
       end
     end,
   }

   sorts.each do |name, sorter|
     canvas = ChunkyPNG::Canvas.new side*colors.size, side
     colors.sort_by(&sorter).each.with_index do |(name, rgba), i|
       canvas.rect i*side, 0, i*side+side-1, side-1, ChunkyPNG::Color::WHITE, ChunkyPNG::Color.rgba(*rgba)
     end
     b64img = Base64.encode64 canvas.to_blob(fast_rgba: true)
     printf "%10s \e]1337;File=preserveAspectRatio=1;inline=1:%s\a\n", name, b64img
   end
   '