Introduction - If you have any usage issues, please Google them yourself
source code for light normalisation presented by Ralph Gross in this paper
@inproceedings{RGross_AVBPA_2003,
author = "Ralph Gross and Vladimir Brajovic",
title = "An Image Preprocessing Algorithm for Illumination Invariant Face Recognition",
booktitle = "4th International Conference on Audio- and Video-Based Biometric Person Authentication (AVBPA)",
month = "June",
year = "2003",
publisher = "Springer"
}