Contour let-BasedMethod for Speckle Reduction with Adaptive Estimation of Noise Level
AL-Rafdain Engineering Journal (AREJ),
Volume 22, Issue 5, Pages 197-211
AbstractSynthetic aperture radar (SAR) and ultrasonic images are inherently affected by speckle noise, which is caused by the coherent nature of the scattering phenomena. This paper presents a contourlet-based method for speckle reduction with an adaptive method for noise-threshold level estimation in a homomorphic framework. The method starts with the generation of many random images simulating the standard deviation level of the log-transformed speckled image. Different contourlet threshold levels are then calculated based on such simulations. Different contourlet coefficients of speckled images are thresholded by their corresponding pre-calculated contourlet thresholds.An exponential operation on the reconstructed output after thresholding is used to simulate the final homomorphic antilog-transformation stage and to obtain the de-speckled images. Unlike other classical and recent de-speckling methods, the despekled images indicate clearly the superiority of the proposed method for speckle reduction, especially for SAR images which possess a lot of detailed textures.
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