Image processing project

[CENTER]السلام عليكم ورحمة الله وبركاته
I’m working on image processing project
Automatic localization of fovea from digital fundus image
using template matching technique
my ques. is how can i build this template
g(i,j)=128 [1-0.5 exp(-(i^2+j^2)\2*segma^2)] where
SIZE=4 are relative to the center of the template[/size]
the template of size 40 * 40
and segma=22
i tried this but i think it not true because the center is not (i,j)


i%Template of macula intensities
for i=1:41
for j=1:41
g(i,j)=128*(1-(0.5*(exp(-((i^2)+ (j^2))/(2*segma^2)))));

waiting 4 reply as soon as possible
thanx in advance
سلام عليكم