Inter Class Variance & Intra Class Variance for Segmented Image

Method to calculate the inter class variance(between classes/segments) and intra class variance(within a particular segment) based on the otsu algorithm.
Main objective of the algorithm is to get a minimum value for intra class variance and maximum value for inter class variance.
In simple words, pixel intensity within a segment must be close to each other while the pixel intensities must be well separated across different segments