Haar wavelets

nAn alternative basis to
express the picture block would be Haar wavelets

n[1,1,1,1],
[1,1,-1,-1], [1,-1,0,0], [0,0,1,-1]

By multiplying the patch by these vectors
we obtain a set of 4 coefficients giving the extent to which each of these
wavelets approximate the image patch

Othogonal but not normalised