TTF のフォントデータから含まれる文字をすべて出力する

ttf-chars.rb

#!/usr/bin/env ruby
#
# base: https://stackoverflow.com/questions/11895641/programmatically-get-a-list-of-characters-a-certain-ttf-font-file-supports
#

require 'ttfunk'

ttf_file = ARGV.shift

ttf = TTFunk::File.open ttf_file
cmap = ttf.cmap

chars = {}
unicode_chars = []

cmap.tables.each do |subtable|
  next if !subtable.unicode?
  chars = chars.merge( subtable.code_map )
end

unicode_chars = chars.keys.map{ |dec| dec.chr("UTF-8") }.uniq
puts unicode_chars.join('')