Parent Topic: ALGORITHM

ENHANCED LEE FILTER

Enhanced Lee filter was modified by Lopes. He propose to divide an image into areas of three classes. The first class corresponds to the homogeneous areas in which the speckles may be eliminated simply by applying an LP filter (or equivalently, averaging, multi-look processing). The second class corresponds to the heterogeneous areas in which the speckles are to be reduced while preserving texture. And the third class are areas containing isolated point targets, which, in this case, the filter should preserve the observed value.

The resulting grey-level value R for the smoothed pixel is:

       R = Im                  for Ci <= Cu
       R = Im * W + Ic * (1-W) for Cu < Ci < Cmax
       R = Ic                  for Ci >= Cmax

where:

       W   =   exp (-DampFactor (Ci-Cu)/(Cmax - Ci))
       Cu  =   SQRT(1/NumberLooks)
       Ci  =   S / Im
       Cmax =  SQRT(1+2/NumberLooks)           
       Ic  =   center pixel in filter window
       Im  =   mean value of intensity within window
       S   =   standard deviation of intensity within window

Parent Topic: ALGORITHM
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