matlab练习程序，求灰度图像最大灰度，最小灰度，平均灰度

cl;
img=imread(\'15.bmp\');
%imshow(img);
[m n]=size(img);
max=0;
min=256;
avg=0;
for i=1:1:m
for j=1:1:n
if img(i,j)<min
            min=img(i,j);
        end
if img(i,j)>max
            max=img(i,j);
        end
        avg=avg+double(img(i,j));
    end
end
%avg=mean(mean(img));
avg=uint8(avg/(m*n));
max
min
avg