Gaussian generalized optimal thresholding algorithm

I need to make a change detection map using thresholding. I have an histogram with 2 noticeable modes (first mod is for unchanged class and the second one for changed pixels) and I have to find the optimal thresholding for this histogram.

In next link you will find the project paper, at the 3rd page is explained the algorithm...I don't even now how to start writing the code. Please, help me! Thnaks in advance..

 https://www.researchgate.net/publication/267099297_Unsupervised_Change_Detection_in_Multitemporal_SAR_Images_Over_Large_Urban_Areas