RubyでAzPainterフォーマットのプレビューをbitmapフアイルに吸出し

gistfile1.rb

#!/usr/bin/env ruby
# vim: fileencoding=utf-8
# AzPainterフォーマットのプレビューをbitmapフアイルに吸出し

module AZPDATA
  FILEHEADER        = "a7c"
  FILEHEADER_LENGTH = 8
  INFOHEADER        = "ISSSSS"
  INFOHEADER_LENGTH = 14
  PREVIEW           = "SSI"
  PREVIEW_LENGTH    = 8

  def read_preview(file)
    width, height = 0
    image = nil
    File.open(file, "rb") do |f|
      head_string, version = f.read(FILEHEADER_LENGTH).unpack(FILEHEADER)
      if head_string == "AZPDATA"
        f.seek(INFOHEADER_LENGTH, IO::SEEK_CUR)
        width, height, image_length = f.read(PREVIEW_LENGTH).unpack(PREVIEW)
        image = f.read(image_length)
      end
    end

    if image.nil?
      nil
    else
      [width, height, image]
    end
  end
  module_function :read_preview
end

module BITMAP
  FILEHEADER        = "a2VIV"
  INFOHEADER        = "VVVvvVVVVVV"
  FILEHEADER_LENGTH = 14
  INFOHEADER_LENGTH = 40
  PLANES            = 1
  BITCOUNT          = 32
  HEADERS_LENGTH    = FILEHEADER_LENGTH + INFOHEADER_LENGTH

  def make(width, height, image)
    buff = ""
    buff << ["\x42\x4d",
           HEADERS_LENGTH + image.length,
           0,
           HEADERS_LENGTH]\
           .pack(FILEHEADER)
    buff << [INFOHEADER_LENGTH,
           width,
           height,
           PLANES,
           BITCOUNT,
           0, 0, 0, 0, 0, 0]\
           .pack(INFOHEADER)
    buff << image
  end
  module_function :make
end

if preview = AZPDATA.read_preview("example.apd")
  File.open("example.apd.bmp", "wb") do |f|
   f.write BITMAP.make(*preview)
  end
else
  warn "error"
  exit 1
end