EXTREMA

        [GREG2\]EXTREMA  [/BLANKING  Bval  Eval]  [/PLOT] [/COMPUTE] [/LOCAL
    PLOT|TERMINAL|FileName]

    Computes and shows the minimum and maximum values of  the  Regular  Grid
    array:  shows XMIN,XMAX,YMIN,YMAX,ZMIN,ZMAX. A useful command for decid-
    ing 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 /LOCAL specifies that instead of computing global  extrema  LOCAL
    extrema values should be computed and:
      - PLOT: 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. /PLOT is an alias for /LOCAL PLOT.
      - TERMINAL: written to the terminal,
      - FileName: written to the given file name.
    These arguments can be combined. If output is TERMINAL  and/or  file,  X
    and Y values are offsets in radians.

    If  option /COMPUTE is not present, the global 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...).