This function returns statistics on the intensity of an image, including the sum, mean, standard deviation, min and max. A rectangular region of interest can be selected by the user by using 'r' as the 2nd parameter. Alternatively, the region of interest can be more accurately defined by a passing its coordinates as a vector.
%IMGSTAT Image statistics
% Returns statistics of an image M, or a portion of it.
% [sum,avg,std,min,max] = imgstat(M)
% [sum,avg,std,min,max] = imgstat(M,'r')
% [sum,avg,std,min,max] = imgstat(M,V)
% returns the stats of the matrix M.
% displays M and lets you select a rectangle for the stats. To
% constrain the rectangle to be a square, use a shift- or right-click
% to begin the drag.
% returns the stats of a portion of M, defined by V.
% V is a four-element vector with the form [xmin ymin width height],
% with the origin being the upper-left corner of the image.