We Ain't Seen Nothin' Yet.

単語のスコア = 単語の出現頻度 * Math.log(Web全体の文書数 / Yahoo!ウェブ検索でのヒット数.to_f)

$KCODE = 'u'  # Yahoo!から返ってくる値の文字コードはUTF-8
require 'net/yjws'

yjws = Net::YJWS::WebSearch.new
yjws.appid = 'gigazine_method_apply_image'  # 自身のAppIDに置き換えてください
yjws.query = 'rails yahoo web services'

results = yjws.execute
results.each{|r| puts "#{r.title}: #{r.url}"}

のほほん徒然 - Haml を実際に Rails で使うチュートリアル: http://d.hatena.ne.jp/uchiuchiyama/20070228/haml_tutorial
第1回 vol. 1 Yahoo! Mail Web Services等 : 秋元@今週の注目サービス : 記事 : MASHUPEDIA - マッシュペディア - : Web API x Mashup: http://www.mashupedia.jp/docs/view/5
日本語で読めるAjax関連情報のリンク集 【▲→川俣晶の縁側→ソフトウェア→技術雑記】: http://mag.autumn.org/Content.modf?id=20050928172048&mf_d=1
のほほん徒然: http://d.hatena.ne.jp/uchiuchiyama/20070228
（..省略..）

$ sudo gem install flickr --include-dependencies

$KCODE = 'u'  # 画像のタイトルなどにマルチバイト文字を含むため
require 'rubygems'  # rubygems経由でインストールした場合
require 'flickr'

# Flickr.initializeメソッドをオーバーライド
# api_keyは自身のAPIkeyに置き換えてください
class Flickr
  def initialize(api_key='4c3c6d6ff60a36824c9d3d8962cadc9e', email=nil, password=nil)
    @api_key = api_key
    @host = 'http://flickr.com'
    @api = '/services/rest'
    login(email, password) if email and password
  end
end

flickr = Flickr.new
# titleやdescription, tagなどに'flower'が含まれる画像を検索
images = flickr.photos(:text => 'flower')
images.each{|image| puts "#{image.title}: #{image.url}"}

Kensington Palace: http://flickr.com/photos/austinevan/1341721206
roses: http://flickr.com/photos/austrianpsycho/1340832029
The Tiniest Wildflower: http://flickr.com/photos/D L Ennis/1341731308
動物園一片小花海: http://flickr.com/photos/旅店/1340831151
(..省略..)

require 'net/yjws'
require 'flickr'

Net::HTTP.version_1_2

module GigazineMethods
  class Image < Flickr

    attr_accessor :text

    def initialize(api_key='4c3c6d6ff60a36824c9d3d8962cadc9e', text=nil)
      @text = text
      @api_key = api_key
      super(api_key)
    end

    def search(text=nil)
      queries = prepare(text)
      options = {'license' => '1,2,3,4,5,6', 'group_id' => '37996572902@N01'}
      phts = []
      begin
        begin
          options['text'] = queries.join(' ')
          phts = photos(options)
          break
        rescue => e
        end
        queries.pop
      end while queries.size != 0
      [phts[rand(phts.size)], queries]
    end

    private

    def prepare(text)
      case text
      when String
        parse(text)
      when Array
        text
      when nil
        if @text.nil?
          ["kyoto", Time.now.strftime("%B")]
        else
          parse(@text)
        end
      else
        text.to_a
      end
    end

    def parse(text)
      appid = 'gigazine_method_apply_image'
      n = 19200000000

      yjws_pos = Net::YJWS::MAService.new
      yjws_pos.appid = appid
      yjws_pos.sentence = text
      yjws_pos.results = 'uniq'
      yjws_pos.uniq_response = 'surface'
      yjws_pos.filter = 9

      yjws_search = Net::YJWS::WebSearch.new
      yjws_search.appid = appid
      yjws_search.results = 1
      yjws_search.similar_ok = 1

      results = yjws_pos.execute[:uniq_result].word_list.sort_by{|e| -e.count}[0, 10].map do |result|
        yjws_search.query = result.surface
        [result.count * Math.log(n / yjws_search.execute.total_results_available.to_f), result.surface]
      end
      results.sort_by{|e| -e[0]}[0, 5].map{|e| e[1]}
    end
  end
end

class Flickr
  def initialize(api_key='4c3c6d6ff60a36824c9d3d8962cadc9e', email=nil, password=nil)
    @api_key = api_key
    @host = 'http://flickr.com'
    @api = '/services/rest'
    login(email, password) if email and password
  end
end

class Flickr::Photo
  def url(size='Medium')
    if size=='Medium'
      owner.photos_url + @id
    else
      sizes(size)['url']
    end
  end

  def source_url(size='Medium')
    @source_url ||= sizes(size)['source']
  end
end

class Net::YJWS::MAService
  def execute
    uri = BASE_URI.dup
    uri.query = to_query
    uniq_result = nil
    Net::HTTP.start(uri.host) do |http|
      response = http.post(uri.path, uri.query)
      src = response.body
      xml = REXML::Document.new(src)
      REXML::XPath.match(xml, "/ResultSet/uniq_result").each {|r|
        uniq_result = Result.new
        uniq_result.total_count    = REXML::XPath.first(r, "total_count").text.to_i
        uniq_result.word_list = []
        REXML::XPath.match(r, "word_list/word").each {|w|
          word = Word.new
          if surface = REXML::XPath.first(w, "surface")
            word.surface = surface.text
          end
          if count = REXML::XPath.first(w, "count")
            word.count = count.text.to_i
          end
          uniq_result.word_list << word
        }
      } # uniq_result
    end
    { :uniq_result=> uniq_result }
  end
end