#include <itkOptAdaptiveHistogramEqualizationImageFilter.h>
Histogram equalization modifies the contrast in an image. The AdaptiveHistogramEqualizationImageFilter is a superset of many contrast enhancing filters. By modifying its parameters (alpha, beta, and window), the AdaptiveHistogramEqualizationImageFilter can produce an adaptively equalized histogram or a version of unsharp mask (local mean subtraction). Instead of applying a strict histogram equalization in a window about a pixel, this filter prescribes a mapping function (power law) controlled by the parameters alpha and beta.
The parameter alpha controls how much the filter acts like the classical histogram equalization method (alpha=0) to how much the filter acts like an unsharp mask (alpha=1).
The parameter beta controls how much the filter acts like an unsharp mask (beta=0) to much the filter acts like pass through (beta=1, with alpha=1).
The parameter window controls the size of the region over which local statistics are calculated.
By altering alpha, beta and window, a host of equalization and unsharp masking filters is available.
For detail description, reference "Adaptive Image Contrast Enhancement using Generalizations of Histogram Equalization." J.Alex Stark. IEEE Transactions on Image Processing, May 2000.