ADAPTIVE-NEIGHBORHOOD FILTERING OF IMAGES CORRUPTED BY SIGNAL-DEPENDENT NOISE

In many image-processing applications the noise that corrupts the imag es is signal dependent, the most widely encountered types being multip licative, Poisson, film-grain, and speckle noise. Their common feature is that the power of the noise is related to the brightness of the co rrupted pixel. This results in brighter areas appearing to be noisier than darker areas. We propose a new adaptive-neighborhood approach to filtering images corrupted by signal-dependent noise. Instead of using fixed-size, fixed-shape neighborhoods, statistics of the noise and th e signal are computed within variable-size, variable-shape neighborhoo ds that are grown for every pixel to contain only pixels that belong t o the same object. Results of adaptive-neighborhood filtering are comp ared with those given by two local-statistics-based filters (the refin ed Lee filter and the noise-updating repeated Wiener filter), both in terms of subjective and objective measures. The adaptive-neighborhood approach provides better noise suppression as indicated by lower mean- squared errors as well as better retention of edge sharpness than the other approaches considered. (C) 1998 Optical Society of America.