Usage: WlzSobel [-o< out object >] [-x] [-y] [-h] [< in object >]
      Options:
      -o Output object file name.
      -x No horizontal pass.
      -y No vertical pass.
      -h Help, prints this usage message.
      Applies a Sobel edge detection filter to the input Woolz object.
      Objects are read from stdin and written to stdout unless the filenames
      are given.
      Example: WlzSobel -o edge.wlz myobj.wlz
      The input Woolz object is read from myobj.wlz, filtered and written
      to edge.wlz.