Sub-samples a woolz interval domain object with grey values.
      Options are:
      -x# Sampling factor for rows (set to 1).
      -y# Sampling factor for columns (set to 1).
      -z# Sampling factor for planes (set to 1).
      -o# Output object file name.
      -a Use max sampling kernel (not set).
      -e Use median sampling kernel (not set).
      -i Use min sampling kernel (not set).
      -g Use gaussian sampling kernel (not set).
      -m Use mean sampling kernel (not set).
      -p Use point sampling (set).
      -h Display this usage information.