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Exact histogram equalization and specification

version (5.58 KB) by Anton Semechko
Perform exact histogram specification or equalization of 2D grayscale images


Updated 04 Sep 2020

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Exact Histogram Specification & Equalization of Grayscale Images

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Histogram equalization is a traditional image enhancement technique which aims to improve visual appearance of the image by assigning equal number of pixels to all available intensity values. Histogram specification is a generalization of histogram equalization and is typically used as a standardization technique to normalize image with respect to a desired probability mass function or properties such as mean intensity, energy and entropy. Unlike classical histogram specification, exact histogram specification algorithm implemented here is able to modify the histogram of any image almost exactly (see snapshot).

The .m file exact_histogram.m is an implementation of an exact histogram specification algorithm described in:

[1] Coltuc D. and Bolon P., 1999, "Strict ordering on discrete images and applications", Proceedings 1999 International Conference on Image Processing

[2] Coltuc D., Bolon P. and Chassery J-M., 2006, "Exact histogram specification", IEEE Transcations on Image Processing 15(5):1143-1152

For a quick demo enter demoHS into Matlab command window.

To access additional information regrading function enter: help exact_histogram


MIT © 2019 Anton Semechko

Cite As

Anton Semechko (2021). Exact histogram equalization and specification (, GitHub. Retrieved .

MATLAB Release Compatibility
Created with R2008a
Compatible with any release
Platform Compatibility
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To view or report issues in this GitHub add-on, visit the GitHub Repository.
To view or report issues in this GitHub add-on, visit the GitHub Repository.