2D Image Subsample
A script that subsamples an 2D matrix (greyscale image).
A = imread('in.jpg');
M = [ 1 4 6 4 1;
4 16 24 16 4;
6 24 36 24 6;
4 16 24 16 4;
1 4 6 4 1 ] / 256;
B = uint8(conv2(double(A),M));
imwrite(B,'out.jpg','JPG');