bif.rb

# BIF Writer for Ruby
# by Derik Olsson <do@derik.co>
# adapted from: bcl's HMS "makeabif.py" script: https://github.com/bcl/HMS/blob/master/scripts/makebif.py

class BIF
  class Writer
    VERSION = 0

    def initialize(options = {})
      if !options[:dir].nil?
        if File.directory?(options[:dir])
          @images = Dir[File.join(options[:dir], '*.jpg')].sort!
          @interval = options.fetch(:interval, '15').to_i * 1000
        else
          puts "INVALID DIRECTORY: #{options[:dir]}"
        end
      else
        puts 'ABORT: Requires directory'
        exit
      end
    end

    def write_bif_file_header(file)
      file << [0x89, 0x42, 0x49, 0x46, 0x0d, 0x0a, 0x1a, 0x0a].pack('C*')
      file << [VERSION, @images.length, @interval].pack('I3')
      file << [].fill(0x00, nil, 44).pack('C*')
    end

    def write_bif_index(file)
      bif_table_size = 8 + (8 * @images.length)
      frame_offset = 64 + bif_table_size
      i = 0

      @images.each do |img|
        file << [i, frame_offset].pack('I2')
        i += 1
        frame_offset += File.new(img).size
      end
      file << [0xffffffff, frame_offset].pack('I2')
    end

    def write_frames(file)
      @images.each do |img|
        file << IO.binread(img)
      end
    end

    def write(filename)
      File.open(filename, 'wb') do |file|
        write_bif_file_header(file)
        write_bif_index(file)
        write_frames(file)
      end
    end
  end
end