
6.3 Sharpening
237
which the count in each histogram bin is incremented or decremented in
proportion to its differences from the counts in the neighboring bins, so
that large counts grow at the expense of smaller counts. When this is done,
the peaks grow into spikes and the valleys are wiped out, as illustrated in
Fig.
11. For further details on this iterative approach see Davis and Rosenfeld
[9] and Peleg [37].
As the examples in Figs. 10 and 11 show, histogram transformations seem
to preserve the appearance of the picture. However, it should be realized
that this is not automatically guaranteed, since there are no constraints on the
transformatio ...