gistfile1.rb

# -*- coding: utf-8 -*-
require 'open-uri'
require 'rubygems'
require 'active_support/core_ext'

class GetQrcode
  API_URL = "http://chart.apis.google.com/chart"
  API_TYPE = "qr"
  IMAGE_SIZE =  "100x100"

  DEFAULT_OPTIONS = {
    :cht => API_TYPE,
    :chs => IMAGE_SIZE
  }

  def initialize(site_url, local_path, options = {})
    @site_url = site_url
    @local_path = local_path
    @options = DEFAULT_OPTIONS.merge(options)
  end

  def get
    api_path = API_URL + '?' + params
    open(api_path) do |qr|
      open(@local_path, 'wb+'){|file| file.write(qr.read) }
    end
  end

  def params
    # sample_url : http://chart.apis.google.com/chart?chs=150x150&cht=qr&chl=http%3a//netafull.jp/hoge?foo=q
    @options.merge(:chl => @site_url).to_param
  end
end

if $0 == __FILE__
  # sample
  get_qrcode = GetQrcode.new('http://google.co.jp', 'test.png')
  get_qrcode.get
end