Haar scaling function φ_j,k(ω) and wavelets . Dark shaded regions correspond to negative constant values, light shaded regions correspond to positive constant values and unshaded regions correspond to zero. The scaling function and wavelets at level j and position k are non-zero on pixel P_j,k only. Pixel P_j,k at level j is subdivided into four pixels at level j + 1, which we label P_j+1,k0, P_j+1,k1, P_j+1,k2 and P_j+1,k3 as defined above.