Which MATLAB function could initialise the parameter for thresholding process based on image intensities

Dear all,

I have a threshold parameter called T, and it converts a green trichromatic coefficient,gbin (gbin = G / R+G+B) to a black and white image.

The main problem is I have different T values for different set of videos.

1) Does MATLAB have a built-in tool to initialise the threshold parameter T based on the histogram distribution of first several images in a video?

2) Which histogram function is the best to initialise the threshold parameter based on the image intensities?

Many thanks. Joe