tests_controller.rb

class TestsController < ApplicationController

  def index
    @callback_url  = "http://127.0.0.1:3000/tests/callback"
    @consumer      = OAuth::Consumer.new("YOUR_APP_KEY","YOUR_APP_SECRET", :authorize_url => "http://www.discogs.com/oauth/authorize", :site => "http://api.discogs.com")
    @request_token = @consumer.get_request_token(:oauth_callback => @callback_url)

    session[:request_token] = @request_token

    redirect_to @request_token.authorize_url(:oauth_callback => @callback_url)
  end

  def callback
    @request_token = session[:request_token]
    @access_token  = @request_token.get_access_token(:oauth_verifier => params[:oauth_verifier])

    send_data @access_token.get("/image/R-150-3492040-1332527654.jpeg").body, :disposition => "inline", :type => "image/jpeg"
  end

end