it is very simple to find correlation between two images of same size.
a=imread('firstimage.tif');
b=imread('secondimage.tif');
if you mean correlation coefficient, you can program manually the function or use corr2 :
corr2(a,b); % returns a scalar
try to read these links also helpful for you
https://www.mathworks.com/matlabcentral/answers/63796-correlation-between-the-two-images
