An objective measurement is proposed to rate the performance in preserving the original brightness. It is referred to as absolute mean brightness error (AMBE) and is defined as the absolute difference between the input and the output image’s mean AMBE = absolute( MB(X) − MB(Y) ) . X and Y denotes the input and output image, respectively. and the MB(.) denotes the process of mean brightness. Lower AMBE indicates that the brightness is better preserved. the input is color image, so i know that the absolute difference between input and output will be in grayscale format. and i want to know how to estimate the mean brightness (MB) for each image. does any one know how to do this in Matlab??