how to calculate mean grey values m1 and m2 for multilevel threshold t1 and t2? can anyone help please!

how to calculate mean grey values m1 and m2 for multilevel threshold t1 and t2? can anyone help please! thresh=multithresh(I,2); seg_I = imquantize(I,thresh); RGB = label2rgb(seg_I); figure, imshow(RGB); is the code after this I need to calculate mean grey values of partitioned two groups like I need to get M1 and M2(mean values) for each portion g1 and g2 respectively.

also need to make the code generic for any kind of given image data set how can I read all images in one go?