Sauvola local image thresholding

Sauvola binarization method is well suited for ill illuminated or stained documents.

The implemented Sauvola method uses integral images for fast computation of the threshold function.

The Sauvola method is described in:

J. Sauvola and M. Pietikainen, Adaptive document image binarization, Pattern Recognition 33, 2000. - http://www.mediateam.oulu.fi/publications/pdf/24.pdf

The modification which uses integral images providing a 20-fold speedup (according to the paper) is described in this paper:

F. Shafait, D. Keysers, and T. M. Breuel, Efficient implementation of local adaptive thresholding techniques using integral images, Document Recognition and Retrieval XV, 2008 - http://www.dfki.uni-kl.de/~shafait/papers/Shafait-efficient-binarization-SPIE08.pdf

A paper evaluating binarization methods:

P. Stathis, E. Kavallieratou and N. Papamarkos - An Evaluation Technique for Binarization Algorithms, Journal of Universal Computer Science, 2008, - http://www.papamarkos.gr/uploaded-files/An%20Evaluation%20Technique%20for%20Binarization%20Algorithms.pdf