how to find the average of an image set

In U<25x1 cell> in each cell consists of < 105 x159 > values i need to find the average of the 25 images how would i find?

Answer 1

[Azzi Abdelmalek]

v=0;
n=numel(U);
for k=1:numel(U)
  v=v+U{k};
end
out=v/n;

%or

out=mean(reshape(cell2mat(U(:))',159,105,[]),3)'

[Image Analyst]

If the images are uint8, be sure to cast to double or else the sum may well clip at 255.

v=v+double(U{k});