Performance evaluation of a feature‐preserving filtering algorithm for removing additive random noise in digital images

Abstract

We evaluate the performance of a feature-preserving filtering algorithm over a range of images corrupted by typical additive random noise against three common spatial filter algorithms: median, sigma and averaging. The concept of the new algorithm is based on a corrupted- pixel identification methodology over a variable subimage size. Rather than processing every pixel indiscriminately in a digital image, this corrupted-pixel identification algorithm interrogates the image in variable-sized subimage regions to determine which are the corrupted pixels and which are not. As a result, only the corrupted pixels are being filtered, whereas the uncorrupted pixels are untouched. Extensive evalu- ation of the algorithm over a large number of noisy images shows that the corrupted-pixel identification algorithm exhibits three major charac- teristics. First, its ability in removing additive random noise is better vi- sually (subjective) and has the smallest mean-square errors (objective) in all cases compared with the median filter, averaging filter and sigma filter. Second, the effect of smoothing introduced by the new filter is minimal. In other words, most edge and line sharpness is preserved. Third, the corrupted-pixel identification algorithm is consistently faster than the median and sigma filters in all our test cases. © 1996 Society of Photo-Optical Instrumentation Engineers. Subject terms: noise removal; feature preserving filtering; corrupted-pixel identi- fication; impulse noise; Gaussian white noise; mean-square error.