encode_image_as_kanji.rb

#!/usr/bin/env ruby
require 'open-uri'
require 'RMagick'

include Magick

COLS = 18
ChannelDepths = [5, 5, 4]

files = []
comment = nil

ARGV.each do |s|
  if File.exist?(s)
    files << s
  else
    comment = s.encode("UTF-8")
  end
end

files.each do |file|
  image = Image::from_blob(open(file, "rb:ASCII-8BIT").read).first.resize_to_fill(COLS)
  [RedChannel, GreenChannel, BlueChannel].zip(ChannelDepths).each {|a| image.set_channel_depth(*a) }
  image = image.quantize(16, RGBColorspace, NoDitherMethod)
  pixels = image.get_pixels(0, 0, COLS, COLS)
  palette = pixels.uniq
  palette_nums = palette.map do |pixel|
    [:red, :green, :blue].zip(ChannelDepths).inject(0) do |result, a|
      (result << a[1]) | (pixel.send(a[0]) >> (QuantumDepth - a[1]))
    end
  end
  pixel_nums = pixels.each_slice(3).map {|a| a.inject(0) {|result, p| (result << 4) | palette.index(p) }}
  if comment
    comment.unpack("U*").first(2 * COLS/3 * COLS / 16).map do |c|
      14.step(0, -2).map {|i| (c >> i) & 0x03 }
    end.flatten.each_with_index {|n, i| pixel_nums[i] |= n << 12 }
  end
  puts (palette_nums + pixel_nums).map {|n| n + 0x4e00 }.pack("U*")
end