download_zip method without temp files

gistfile1.rb

def download_zip(image_list)
  unless image_list.blank?
    file_name = 'pictures.zip'

    stringio = Zip::ZipOutputStream::write_buffer do |z|
      image_list.each do |img|
        title = img.title
        title += '.jpg' unless title.end_with?('.jpg')

        z.put_next_entry(title)
        z.print IO.read(img.path)
      end
    end
  
    send_data stringio.string, :type => 'application/zip', :disposition => 'attachment', :filename => file_name
  end
end