In this paper, a new homomorphic wavelet-based de-speckling technique is proposed. The technique combines a spatial domain processing with another transform domain processing in a homomorphic environment. The spatial domain nonlinear processing is based on replacing each log-transformed pixel value of the speckled image by a weighted-average of the log-transformed pixel values in the neighborhood of that pixel. The weighted averaged log-transformed image is then subjected to wavelet thresholding for further nonlinear transform domain processing. An exponential operation on the filtered output is used to simulate the final homomorphic antilog-transformation stage and to obtain the de-speckled image. Quantitative and qualitative measures prove the superiority of the proposed technique for the applications of image classification and recognition in ultrasonic and SAR systems.
Keywords: Speckle noise, homomorphic environment, weighted-average, wavelet thresholding