information:classification
Decoding

f x, y = 1 4 ∑ u = 0 7 ∑ v = 0 7 α (u) α (v) F u, v cos cos {\displaystyle f_{x,y}={\frac {1}{4}}\sum _{u=0}^{7}\sum _{v=0}^{7}\alpha (u)\alpha (v)F_{u,v}\cos \left\cos \left}