Image contrast enhancement using homomorphic processing and adaptive filters

Abstract

This paper proposes a method of image enhancement using adaptive filters. An adaptive high pass (HP) and low pass (LP) filters are combined in homomorphic domain to obtain adaptive image enhancement filter. The method offers great advantages over the method of using fixed filters. Adaptive filters allow the use of HPF with different sizes and amount of sharpening as required. Also this paper proposes spatial domain contrast enhancement method which is equivalent to the processing in homomorphic domain without the need to any logarithmic operations. The use of adaptive HP method is shown to be very useful and avoids the noise amplification and details blurring. The adaptive method do not assume any knowledge about the image statistics or characteristics. Results are presented to illustrate the performance of the proposed method. Future research includes studying the use of multiple HPF channels with different HP filter sizes and the adaptation of the enhancement parameters to the changes in the image local contrast.