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Summary: IEEE TRANSACTIONS ON IMAGE PROCESSING, VOL. 10, NO. 1, JANUARY 2001 179
of the median filter, which is used for preliminary processing in most
of the state-of-the-art impulsive noise filters. Our first tests on syn-
thetic and natural images demonstrated that the peak-and-valley filter
and the median filter have comparable performances. The median filter
is slightly better than the peak-and-valley filter at detecting/correcting
noisy pixels, but on the other hand it tends to alter more true pixels.
Nevertheless, even if the amount of true pixel alterations is signifi-
cant (more than 63% for the median filter was recorded), the average
change is rather small (no more than 11 were recorded). In some ap-
plications this degradation of the image, a milt smoothing, could not
readily justify a heavy computational method to discriminate between
noisy and true pixels, especially when dealing with video processing.
The peak-and-valley filter demonstrated to be much faster than the me-
dian filter for all types of images tested.
The peak-and-valley filter represents an interesting replacement for
the median filter in those more sophisticated, and consequently more
performant filtering methods, in order to improve their efficiency.
REFERENCES
[1] A. Beläid and A. Beläid, "Reconnaissance des formes: Méthodes et ap-
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