RubyでPNGにLibreOffice Drawのodgファイルを埋め込んで再編集可能にする

png_odg.rb

require "base64"
require "json"

require "bundler/inline"
gemfile do
  source "https://rubygems.org"
  gem "chunky_png", "1.4.0"
end

KEYWORD_EMBEDDED_SOURCE = "Embedded Source"

EmbeddedSourceContent = Struct.new(:type, :filename, :file)

def cmd_embed(f_png, f_odg)
  odg_data = File.binread(f_odg)
  odg_b64str = Base64.encode64(odg_data)

  esc = EmbeddedSourceContent.new(
    ".odg",
    File.basename(f_odg),
    odg_b64str
  )

  f_out = f_png.delete_suffix(".png") + ".odg.png"

  image = ChunkyPNG::Image.from_file(f_png)
  image.metadata[KEYWORD_EMBEDDED_SOURCE] = JSON.generate(esc.to_h)
  image.save(f_out)
end

def cmd_extract(f_png, f_odg = nil)
  image = ChunkyPNG::Image.from_file(f_png)
  json = image.metadata[KEYWORD_EMBEDDED_SOURCE]
  esc = EmbeddedSourceContent.new(**JSON.parse(json))
  odg_data = Base64.decode64(esc.file)

  f_out = f_odg || esc.filename
  File.binwrite(f_out, odg_data)
end

def print_help
  this_cmd = $0
  puts <<~HELP
    USAGE:
      ruby #{this_cmd} embed {f_png} {f_odg}
      ruby #{this_cmd} extract {f_png} [f_odg_output]
  HELP
end

def main(args)
  case args[0]
  when "em", "embed"
    args.shift
    f_png = args.shift
    f_odg = args.shift
    cmd_embed(f_png, f_odg)
  when "ex", "extract"
    args.shift
    f_png = args.shift
    f_odg = args.shift
    cmd_extract(f_png, f_odg)
  when "-h", "--help"
    print_help
  else
    print "invalid arguments\n\n"
    print_help
    exit 1
  end
end

main(ARGV)

RubyでPNGにLibreOffice Drawのodgファイルを埋め込んで再編集可能にする
https://qiita.com/sonota88/items/8d64cd21ce2fc14bf5ed