mini_exiftool.rb

# -- encoding: utf-8 --
#
# MiniExiftool
#
# This library is wrapper for the Exiftool command-line
# application (http://www.sno.phy.queensu.ca/~phil/exiftool/)
# written by Phil Harvey.
# Read and write access is done in a clean OO manner.
#
# Author: Jan Friedrich
# Copyright (c) 2007-2012 by Jan Friedrich
# Licensed under the GNU LESSER GENERAL PUBLIC LICENSE,
# Version 2.1, February 1999
#

require 'fileutils'
require 'tempfile'
require 'pstore'
require 'set'
require 'shellwords'
require 'time'

# Simple OO access to the Exiftool command-line application.
class MiniExiftool

  # Name of the Exiftool command-line application
  @@cmd = 'exiftool'

  # Hash of the standard options used when call MiniExiftool.new
  @@opts = { :numerical => false, :composite => true, :convert_encoding => false, :timestamps => Time }

  attr_reader :filename
  attr_accessor :numerical, :composite, :convert_encoding, :errors, :timestamps

  VERSION = '1.4.4'

  # +opts+ support at the moment
  # * <code>:numerical</code> for numerical values, default is +false+
  # * <code>:composite</code> for including composite tags while loading,
  #   default is +true+
  # * <code>:convert_encoding</code> convert encoding (See -L-option of
  #   the exiftool command-line application, default is +false+
  # * <code>:timestamps</code> generating DateTime objects instead of
  #   Time objects if set to <code>DateTime</code>, default is +Time+
  #
  #   <b>ATTENTION:</b> Time objects are created using <code>Time.local</code>
  #   therefore they use <em>your local timezone</em>, DateTime objects instead
  #   are created <em>without timezone</em>!
  def initialize filename=nil, opts={}
    opts = @@opts.merge opts
    @numerical = opts[:numerical]
    @composite = opts[:composite]
    @convert_encoding = opts[:convert_encoding]
    @timestamps = opts[:timestamps]
    @values = TagHash.new
    @tag_names = TagHash.new
    @changed_values = TagHash.new
    @errors = TagHash.new
    load filename unless filename.nil?
  end

  def initialize_from_hash hash # :nodoc:
    hash.each_pair do |tag,value|
      set_value tag, value
    end
    set_attributes_by_heuristic
    self
  end

  # Load the tags of filename.
  def load filename
    unless filename && File.exist?(filename)
      raise MiniExiftool::Error.new("File '#{filename}' does not exist.")
    end
    if File.directory?(filename)
      raise MiniExiftool::Error.new("'#{filename}' is a directory.")
    end
    @filename = filename
    @values.clear
    @tag_names.clear
    @changed_values.clear
    opt_params = ''
    opt_params << (@numerical ? '-n ' : '')
    opt_params << (@composite ? '' : '-e ')
    opt_params << (@convert_encoding ? '-L ' : '')
    cmd = %Q(#@@cmd -q -q -s -t #{opt_params} #{@@sep_op} #{Shellwords.escape(filename)})
    if run(cmd)
      parse_output
    else
      raise MiniExiftool::Error.new(@error_text)
    end
    self
  end

  # Reload the tags of an already read file.
  def reload
    load @filename
  end

  # Returns the value of a tag.
  def [] tag
    @changed_values[tag] || @values[tag]
  end

  # Set the value of a tag.
  def []=(tag, val)
    @changed_values[tag] = val
  end

  # Returns true if any tag value is changed or if the value of a
  # given tag is changed.
  def changed? tag=false
    if tag
      @changed_values.include? tag
    else
      !@changed_values.empty?
    end
  end

  # Revert all changes or the change of a given tag.
  def revert tag=nil
    if tag
      val = @changed_values.delete(tag)
      res = val != nil
    else
      res = @changed_values.size > 0
      @changed_values.clear
    end
    res
  end

  # Returns an array of the tags (original tag names) of the read file.
  def tags
    @values.keys.map { |key| @tag_names[key] }
  end

  # Returns an array of all changed tags.
  def changed_tags
    @changed_values.keys.map { |key| MiniExiftool.original_tag(key) }
  end

  # Save the changes to the file.
  def save
    return false if @changed_values.empty?
    @errors.clear
    temp_file = Tempfile.new('mini_exiftool')
    temp_file.close
    temp_filename = temp_file.path
    FileUtils.cp filename, temp_filename
    all_ok = true
    @changed_values.each do |tag, val|
      original_tag = MiniExiftool.original_tag(tag)
      arr_val = val.kind_of?(Array) ? val : [val]
      arr_val.map! {|e| convert e}
      tag_params = ''
      arr_val.each do |v|
        tag_params << %Q(-#{original_tag}=#{Shellwords.escape(v.to_s)} )
      end
      opt_params = ''
      opt_params << (arr_val.detect {|x| x.kind_of?(Numeric)} ? '-n ' : '')
      opt_params << (@convert_encoding ? '-L ' : '')
      cmd = %Q(#@@cmd -q -P -overwrite_original #{opt_params} #{tag_params} #{temp_filename})
      if convert_encoding && cmd.respond_to?(:encode)
        cmd.encode('ISO-8859-1')
      end
      result = run(cmd)
      unless result
        all_ok = false
        @errors[tag] = @error_text.gsub(/Nothing to do.\n\z/, '').chomp
      end
    end
    if all_ok
      FileUtils.cp temp_filename, filename
      reload
    end
    temp_file.delete
    all_ok
  end

  # Returns a hash of the original loaded values of the MiniExiftool
  # instance.
  def to_hash
    result = {}
    @values.each do |k,v|
      result[@tag_names[k]] = v
    end
    result
  end

  # Returns a YAML representation of the original loaded values of the
  # MiniExiftool instance.
  def to_yaml
    to_hash.to_yaml
  end

  # Create a MiniExiftool instance from a hash
  def self.from_hash hash
    instance = MiniExiftool.new
    instance.initialize_from_hash hash
    instance
  end

  # Create a MiniExiftool instance from YAML data created with
  # MiniExiftool#to_yaml
  def self.from_yaml yaml
    MiniExiftool.from_hash YAML.load(yaml)
  end

  # Returns the command name of the called Exiftool application.
  def self.command
    @@cmd
  end

  # Setting the command name of the called Exiftool application.
  def self.command= cmd
    @@cmd = cmd
  end

  # Returns the options hash.
  def self.opts
    @@opts
  end

  # Returns a set of all known tags of Exiftool.
  def self.all_tags
    unless defined? @@all_tags
      @@all_tags = pstore_get :all_tags
    end
    @@all_tags
  end

  # Returns a set of all possible writable tags of Exiftool.
  def self.writable_tags
    unless defined? @@writable_tags
      @@writable_tags = pstore_get :writable_tags
    end
    @@writable_tags
  end

  # Returns the original Exiftool name of the given tag
  def self.original_tag tag
    unless defined? @@all_tags_map
      @@all_tags_map = pstore_get :all_tags_map
    end
    @@all_tags_map[tag]
  end

  # Returns the version of the Exiftool command-line application.
  def self.exiftool_version
    output = `#{MiniExiftool.command} -ver 2>&1`
    unless $?.exitstatus == 0
      raise MiniExiftool::Error.new("Command '#{MiniExiftool.command}' not found")
    end
    output.chomp!
  end

  def self.unify tag
    tag.to_s.gsub(/[-_]/,'').downcase
  end

  # Exception class
  class MiniExiftool::Error < StandardError; end

  ############################################################################
  private
  ############################################################################

  @@error_file = Tempfile.new 'errors'
  @@error_file.close

  if Float(exiftool_version) < 7.41
    @@separator = ', '
    @@sep_op = ''
  else
    @@separator = '@@'
    @@sep_op = '-sep @@'
  end

  def run cmd
    if $DEBUG
      $stderr.puts cmd
    end
    @output = `#{cmd} 2>#{@@error_file.path}`
    if convert_encoding && @output.respond_to?(:force_encoding)
      @output.force_encoding('ISO-8859-1')
    end
    @status = $?
    unless @status.exitstatus == 0
      @error_text = File.readlines(@@error_file.path).join
      return false
    else
      @error_text = ''
      return true
    end
  end

  def convert val
    case val
    when Time
      val = val.strftime('%Y:%m:%d %H:%M:%S')
    end
    val
  end

  def method_missing symbol, *args
    tag_name = symbol.id2name
    if tag_name.sub!(/=$/, '')
      self[tag_name] = args.first
    else
      self[tag_name]
    end
  end

  def parse_output
    @output.each_line do |line|
      tag, value = parse_line line
      set_value tag, value
    end
  end

  def parse_line line
    if line =~ /^([^\t]+)\t(.*)$/
      tag, value = $1, $2
      case value
      when /^\d{4}:\d\d:\d\d \d\d:\d\d:\d\d/
        s = value.sub(/^(\d+):(\d+):/, '\1-\2-')
        begin
          if @timestamps == Time
            value = Time.parse(s)
            elsif @timestamps == DateTime
            value = DateTime.parse(s)
          else
            raise MiniExiftool::Error.new("Value #@timestamps not allowed for option timestamps.")
          end
        rescue ArgumentError
          value = false
        end
      when /^\d+\.\d+$/
        value = value.to_f
      when /^0+[1-9]+$/
        # nothing => String
      when /^-?\d+$/
        value = value.to_i
      when /^[\d ]+$/
        # nothing => String
      when /#{@@separator}/
        value = value.split @@separator
      end
    else
      raise MiniExiftool::Error.new("Malformed line #{line.inspect} of exiftool output.")
    end
    return [tag, value]
  end

  def set_value tag, value
    @tag_names[tag] = tag
    @values[tag] = value
  end

  def set_attributes_by_heuristic
    self.composite = tags.include?('ImageSize') ? true : false
    self.numerical = self.file_size.kind_of?(Integer) ? true : false
    # TODO: Is there a heuristic to determine @convert_encoding?
    self.timestamps = self.FileModifyDate.kind_of?(DateTime) ? DateTime : Time
  end

  def temp_filename
    unless @temp_filename
      temp_file = Tempfile.new('mini-exiftool')
      temp_file.close
      FileUtils.cp(@filename, temp_file.path)
      @temp_filename = temp_file.path
    end
    @temp_filename
  end

  def self.pstore_get attribute
    load_or_create_pstore unless defined? @@pstore
    result = nil
    @@pstore.transaction(true) do |ps|
      result = ps[attribute]
    end
    result
  end

  def self.load_or_create_pstore
    # This will hopefully work on *NIX and Windows systems
    home = ENV['HOME'] || ENV['HOMEDRIVE'] + ENV['HOMEPATH'] || ENV['USERPROFILE']
    subdir = RUBY_PLATFORM =~ /\bmswin/i ? '_mini_exiftool' : '.mini_exiftool'
    FileUtils.mkdir_p(File.join(home, subdir))
    filename = File.join(home, subdir, 'exiftool_tags_' << exiftool_version.gsub('.', '_') << '.pstore')
    @@pstore = PStore.new filename
    if !File.exist?(filename) || File.size(filename) == 0
      @@pstore.transaction do |ps|
        ps[:all_tags] = all_tags = determine_tags('list')
        ps[:writable_tags] = determine_tags('listw')
        map = {}
        all_tags.each { |k| map[unify(k)] = k }
        ps[:all_tags_map] = map
      end
    end
  end

  def self.determine_tags arg
    output = `#{@@cmd} -#{arg}`
    lines = output.split(/\n/)
    tags = Set.new
    lines.each do |line|
      next unless line =~ /^\s/
      tags |= line.chomp.split
    end
    tags
  end


  # Hash with indifferent access:
  # DateTimeOriginal == datetimeoriginal == date_time_original
  class TagHash < Hash # :nodoc:
    def[] k
      super(unify(k))
    end
    def []= k, v
      super(unify(k), v)
    end
    def delete k
      super(unify(k))
    end

    def unify tag
      MiniExiftool.unify tag
    end
  end

end