Thresholding, the problem of pixel classification is attempted here us
ing fuzzy clustering algorithms. The segmented regions are fuzzy subse
ts, with soft partitions characterizing the region boundaries. The val
idity of the assumptions and thresholding schemes are investigated in
the presence of distinct region proportions. The hard k means and fuzz
y c means algorithms have been found useful when object and background
regions are well balanced. Fuzzy thresholding is also formulated as e
xtraction of normal densities to provide optimal partitions. Regional
imbalances in gray distributions are taken care of in region normalize
d histograms. (C) 1997 Pattern Recognition Society. Published by Elsev
ier Science Ltd.