Thresholding is a very basic operation in image processing. And, a good algorithm always begins with a good basis! Otsu thresholding is a simple yet effective global automatic thresholding method for binarizing grayscale images such as foregrounds and backgrounds.Speed: Because Otsu threshold operates on histograms (which are integer or float arrays of length 256), it’s quite fast
Reference & Information
http://www.labbookpages.co.uk/software/imgProc/otsuThreshold.html