         "#{img_path(project, image_id)}/#{z_index}/#{x_index}/#{y_index}.png"
       ]
     }
-    {_, status} = System.cmd(cmd, args)
+    {_, status} = System.cmd cmd, args
     status
   end
-end+end

         rescale,
         z_index,
         %{x_index: x_index, y_index: y_index, x_pos: x_pos, y_pos: y_pos}) do

    x_folder = Path.join [@imageroot, project, image_id, z_index, x_index]
    File.mkdir_p x_folder

    {cmd, args} = {

  Returns true if everything went fine
  """
  def rescale(project, image_id, rescale) do
    source_img_path = Path.absname(Path.join([@imageroot, project, "sources", image_id]))
    target_dir = Path.join([@imageroot, project, image_id])
    File.mkdir_p target_dir # todo do in caller
    
    {cmd, args} = {
      @im_cmd,
      [
        source_img_path,
        "-scale",
        "#{rescale}x#{rescale}",
        "#{img_path(project, image_id)}/#{image_id}.#{rescale}.#{@intermediate_format_suffix}"
      ]
    }
    {_, status} = System.cmd cmd, args
    status == 0
  end

