SMOOTH

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SMOOTH

            SMOOTH

        Smooths an input map  using  various  methods,  all  based  upon  a con-
        volving  kernel  of  5  points large only.  This method  is  crude,  but
        very fast,  and  supports  blanking  in  principle...   Data  cubes  are
        processed plane by plane.

          1.  BOX A simple 5 by 5 boxcar smoothing.  This is   a   very   strong
            smoothing...
          2.   GAUSS A gaussian smoothing.  The gaussian is sampled on a 5  by 5
            grid  so it must not be too broad.  3 pixels seem  a  maximum.   Use
            task  GAUSS_SMOOTH  if you want  to  smooth  with  a  broader gauss-
            ian,  but  beware  it  does  not  handle  properly blanked pixels.
          3.  HANNING Smoothing by a 5 by 5 pyramid, with weights 3 2 1.
          4.  USER User defined smoothing coefficients on  a  5   by   5   grid,
            assuming   biaxial  symmetry.   Hence  6  coefficients  only are re-
            quired, S00 S10 S11 S20 S21 S22.  The corresponding smoothing kernel
            is :
                                    S22 S21 S20 S21 S22
                                    S21 S11 S10 S11 S21
                                    S20 S10 S00 S10 S20
                                    S21 S11 S10 S11 S21
                                    S22 S21 S20 S21 S22
            Such  a  generalised  "smoothing"  enables  some  image  enhancement
            based  on  gradients  (e.g.   with  weights 4 -1  0  0  0  0).   The
            "smoothed"  image is normalised by the sum of absolute values of the
            coefficients.