WallpaperRetriever.rb

#!/usr/bin/env ruby
# Retrieves all National Geographic Photo-contest wallpapers from 2008 and 2009
# Original scripts from: http://www.webupd8.org/2009/11/automatically-download-all-wallpapers.html

require 'net/http'

class WallpaperRetriever
  attr_reader :destination_folder,:urls

  def initialize(destination="~/Pictures/Wallpapers/NationalGeographic/")
    @destination_folder = File.expand_path(destination)
    @url_mappings = {}
    create_destination_folder
  end

  def create_destination_folder
    `mkdir -p #{destination_folder}` unless File.exists?(destination_folder)
  end

  def download_all
    get_wallpaper_urls
    @url_mappings.each do |url,v|
      dateyear = "%s%s" % [v[:year],v[:date]]
      entry = v[:entry]
      destination = File.join(destination_folder,"#{dateyear}-#{entry}.jpg")
      puts "Testing #{url}"
      unless File.exists?(destination)
        if Net::HTTP.start("ngm.nationalgeographic.com",80){|http| http.head(url.gsub("http://ngm.nationalgeographic.com",''))}.code.to_i == 200
          puts "Retrieving entry #{entry} from #{dateyear} (#{url}) to #{destination}"
          puts `wget -U -q "Mozilla" -O "#{destination}" --referer="#{url}" "#{url}"`
        end
      end
    end
  end

  private  
  # Specifying a resolution only affects 2008, since 2009 only has 1600px width wallpapers
  # only valid resolutions for 2008 are 1280 (default), 1024 and 800.
  def get_wallpaper_urls(resolution=1280)
    dates_2008 = %w[1107 1103 1027 1020 1014 1006 0929 0922 0915 0908 0901 0825 0818 0811]
    dates_2009 = %w[1109 1102 1026 1019 1013 1005 0928 0921 0914 0907 0831 0824 0817]

    dates_2008.map do |date|
      (1..26).each do |entry|
        url = "http://ngm.nationalgeographic.com/photo-contest/img/wallpaper/#{date}wallpaper-#{entry}_#{resolution}.jpg"
        destination = File.join(destination_folder,"2008#{date}-#{entry}.jpg")
        @url_mappings[url] = {:year => 2008, :date => date, :entry => entry}
      end
    end

    dates_2009.map do |date|
      (1..26).each do |entry|
        url = "http://ngm.nationalgeographic.com/photo-contest/2009/img/wallpaper/#{date}wallpaper-#{entry}_1600.jpg"
        @url_mappings[url] = {:year => 2009, :date => date, :entry => entry}
      end
    end
  end
end

WallpaperRetriever.new.download_all
exit