A new despeckling algorithm based on region subdivision(DABRS)is presented to effectively preserve edge characteristics and to improve the performance of reducing multiplicative speckle noise in synthetic aperture radar(SAR). Gaussian-Gamma-shaped bi-windows with different orientations are used to obtain the edge strength map(ESM)by ratio operations. Then
the threshold-processing ESM is used to divide a SAR image into different regions. Two improved filters
the Kuan filter with variable-size windows and the Sigma filter
are used to reduce speckle in homogeneous and edge regions
respectively. Iteration filtering strategy is adopted by the two improved filters to smooth speckle better
and the window size of improved Kuan filter increases with iteration progressing. Experimental results and comparisons with most existing despeckling algorithms show that the DABRS has advantages in the speckle suppression and edge preservation
improves the equivalent number of looks by more than 30%
increases the edge keep index by more than 8%
and has more smooth visual effects in the homogeneous regions of despeckling images.
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references
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