def crop!( options = {} )
        # setup the default params
        options[:crop_left]   ||= 0
        options[:crop_top]    ||= 0
        options[:crop_width]  ||= 100
        options[:crop_height] ||= 100
        # passed params could be strings, so convert them to ints/booleans
        crop_l = options[:crop_left].to_i
        crop_t = options[:crop_top].to_i
        crop_w = options[:crop_width].to_i
        crop_h = options[:crop_height].to_i
 
        # call the appropriate crop method for the image processor we're using with attachment_fu
         crop_with_paperclip! crop_l, crop_t, crop_w, crop_h
  end
 
  def crop_with_paperclip!(crop_l, crop_t, crop_w, crop_h)   
        dst = Tempfile.new("stream")
        dst.binmode  
        src = File.join(RAILS_ROOT, "public/#{self.photo.url(:large)}")
        command = <<-end_command
          #{ Paperclip.path_for_command('convert') }
          "#{src}"
          -crop "#{crop_w}x#{crop_h}+#{crop_l}+#{crop_t}"
          "#{File.expand_path(dst.path)}"
        end_command
        
        success = system(command.gsub(/\s+/, " "))
 
        if success && $?.exitstatus != 0
          raise PaperclipError, "There was an error processing this thumbnail"
        end
 
        thumb = Paperclip::Thumbnail.make(dst, "48x48#", nil, true)  
 
        thumb_path = File.join(RAILS_ROOT, "public/#{self.photo.url(:thumb)}")
        begin
          FileUtils.rm(thumb_path) if File.exist?(thumb_path)
        rescue Errno::ENOENT => e
          # ignore file-not-found, let everything else pass
        end
 
        result = thumb.stream_to(thumb_path)
        thumb.close
        result.close   
   end