BACKGROUND
Keywords: greg

Next: CIRCLE Up: Image Analysis Tasks Previous: image-analysis Contents Index

##
BACKGROUND

            BACKGROUND

        Computes the background image of a given map.  The basic idea is to make
        a  crude  mesh  model of the background by finding the most likely value
        of  the  original map (within some intensity range) for each cell of the
        crude  mesh.  The most likely value is found by making an  histogram  of
        the  intensity  distribution  in the  specified  range  for  all  points
        lying  in  a circle around the cell center.  The circle may (and should)
        be greater than the cell size.  If  the  number  of  pixels  within  the
        intensity range is too small, no value is attributed to the intermediate
        mesh.

        The  intermediate  model  is then resampled to the original map  using a
        general   triangulation   technique.   This  procedure  has  several ad-
        vantages  over  a simpler method which would compute a "smoothed"  image
        as  the background, because it is not biased by any emission outside the
        selected range, and it is able to interpolate  over  large  non  sampled
        area of the intermediate mesh.  Other tasks with similar names use other
        interpolation algorithms.  They will hopefully be merged into  a  single
        task one (with a switch for the interpolation algorithm).

        CAUTION:  In the present version, blanking in the  input  image  is  not
        correctly  handled.  This can usually be worked around by specifiying an
        apropriate range.