<threshold map="diag5x5" alias="diag">
    <description>Simple Diagonal Line Dither</description>
    <levels width="5" height="5" divisor="6">
        4 2 1 3 5
        2 1 3 5 4
        1 3 5 4 2
        3 5 4 2 1
        5 4 2 1 3
    </levels>
  </threshold>