visitor_pass

# coding: utf-8

class VisitorPassController < ApplicationController
  def create_pass
    visitor = Visitor.find(params[:id])
    report = ThinReports::Report.new layout: File.join(Rails.root, 'app', 'reports', 'visitor_pass.tlf')
    report.start_new_page do |page|
      # jpg_filepath method will return the path of JPEG file.
      #   e.g. "Rails.root/photos/visitor_001.jpg"
      page.item(:photo).src(visitor.jpg_filepath)
      page.values name: visitor.name
    end

    send_data report.generate, filename: 'visitor_pass.pdf', type: 'application/pdf', disposition: 'attachment'
  end
end

あとはこんな文章を追加する感じ？

In addition, see also the following links:
http://prawn.majesticseacreature.com/docs/0.11.1/Prawn/Images.html#method-i-image

Prawn is a library that is used internally to generate the PDF in thinreports.
So, item#src method of thinreports is almost the same as method of that.