picasa_download.rb

# Backs up all the photos from Google Picasa Web Albums.
#
# The script downloads the original version of the photos, and is not limited to
# 1600x1200 thumbnails.
#
# Author:: Victor Costan
# Copyright:: Copyright (C) 2010 Victor Costan
# License:: MIT

require 'yaml'

# Requires RubyGems and the GData gem.
require 'rubygems'
require 'gdata'

# Creates a GData client for picasa.
#
# config_path should point to a yaml file that looks like this:
#     username: costan
#     password: "secret"
def picasa_client(config_path)
  account = File.open(config_path, 'r') { |f| YAML.load f }
  client = GData::Client::Photos.new
  client.clientlogin(account['username'], account['password'])
  client
end

# Retrieves all albums for a user.
def picasa_albums(client, user = nil)
  uri = "http://picasaweb.google.com/data/feed/api/user/#{user || 'default'}"
  feed = client.get(uri).to_xml
  albums = []
  feed.elements.each('entry') do |entry|
    next unless entry.elements['gphoto:id']
    albums << { :id => entry.elements['gphoto:id'].text,
                :user => entry.elements['gphoto:user'].text,
                :title => entry.elements['title'].text }
  end
  albums
end

# Retrieves all photos from an album.
def picasa_photos(client, album)
  uri = "http://picasaweb.google.com/data/feed/api/user/" +
        "#{album[:user] || 'default'}/albumid/#{album[:id]}?kind=photo&imgmax=d"
  
  feed = client.get(uri).to_xml
  photos = []
  feed.elements.each('entry') do |entry|
    next unless entry.elements['gphoto:id']
    next unless entry.elements['media:group']
    
    photo = { :id => entry.elements['gphoto:id'].text,
              :album_id => entry.elements['gphoto:albumid'].text,
              :title => entry.elements['title'].text }
    entry.elements['media:group'].elements.each('media:content') do |content|
      photo[:url] = content.attribute('url').value
    end
    photos << photo
  end
  photos
end

if $0 == __FILE__
  client = picasa_client 'account.yml'
  albums = picasa_albums client
  dir_name = "picasa_#{albums.first[:user]}"
  Dir.mkdir dir_name
  Dir.chdir dir_name
  albums.each do |album|
    Dir.mkdir album[:title]
    Dir.chdir album[:title] do
      print "Album #{album[:title]}\n"
      photos = nil
      until photos
        begin
          photos = picasa_photos client, album
        rescue GData::Client::ServerError
          "Server error, retrying\n"
        end
      end
      
      photos.each do |photo|
        print "#{album[:title]}/#{photo[:title]}\n"        
        response = nil
        until response
          begin
            response = client.get photo[:url]
          rescue GData::Client::ServerError
            "Server error, retrying\n"
          end
        end
        
        File.open(photo[:title], 'w') { |f| f.write response.body }
      end
    end
  end
end