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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.



Gildas manager 2020-09-28