The median filter, in which each pixel is replaced by the median of nearby values is
suitable to remove additive noise from an image.
The Lee filter reduces the speckle noise by applying a spatial filter to each pixel
in an image, which filters the data based on local statistics calculated within a
square window. The value of the center pixel is replaced by a value calculated
using the neighboring pixels. Use the Lee filter to smooth speckled data that has
a multiplicative component.
The Enhanced Lee filter is a refined version of the Lee filter, reducing the speckle
noise effectively by preserving image sharpness and detail. Use the Enhanced Lee filter
to reduce speckle while preserving texture information.
The Kuan filter follows a similar filtering process to the Lee filter in reducing
speckle noise. This filter also applies a spatial filter to each pixel in an image,
filtering the data based on local statistics of the centered pixel value that is
calculated using the neighboring pixels.
Nathan filter is a particular case of the Kuan filter, obtained by puting looks
= 1
, and is thus applicable to 1-look SAR images only.
The size of the pixel window used to each filter is 3-by-3.