EXTREMA

        [GREG2\]EXTREMA [/BLANKING Bval Eval] [/PLOT]  [/COMPUTE]

    Computes and shows the minimum and maximum values of  the  Regular  Grid
    array:   shows   XMIN,XMAX,YMIN,YMAX,ZMIN,ZMAX.  A  useful  command  for
    deciding where to set contour levels, or what size to give to the BOX if
    you  want  an  exact  aspect ratio between two coordinates.  The current
    blanking value is used, but can be overridden  using  option  /BLANKING.
    Option  /PLOT  specifies  that instead of computing global extrema LOCAL
    extrema values should be computed, and written at appropriate places  on
    the plot. This is a very good way to avoid ambiguities in contour map. A
    shortest format is used for writing the values, and the  character  size
    controls the label size.  If Option /COMPUTE is not present, the extrema
    are only computed if not already known (from a previous call to EXTREMA,
    or  from  an  image  header).  /COMPUTE forces computation from the data
    array. It should be used  if  for  any  reason  the  known  extrema  are
    incorrect  (invalid  image  header, killed bad pixel, change of blanking
    value...).