# HistEQ node¶

This documentation is for version 2.0 of HistEQ (net.sf.cimg.CImgHistEQ).

## Description¶

Equalize histogram of brightness values.

Uses the ‘equalize’ function from the CImg library on the ‘V’ channel of the HSV decomposition of the image.

CImg is a free, open-source library distributed under the CeCILL-C (close to the GNU LGPL) or CeCILL (compatible with the GNU GPL) licenses. It can be used in commercial applications (see http://cimg.eu).

## Inputs¶

Input Description Optional
Source   No
NbLevels / nb_levels Integer 4096 Number of histogram levels used for the equalization.
(Un)premult / premult Boolean Off Divide the image by the alpha channel before processing, and re-multiply it afterwards. Use if the input images are premultiplied.
Invert Mask / maskInvert Boolean Off When checked, the effect is fully applied where the mask is 0.
Mix / mix Double 1 Mix factor between the original and the transformed image.