for l in range(7):
    x, y, z, t = 0,0,0,0
    for m in range(a.shape[0]):
        for n in range(a.shape[1]):
            for o in range(256*l,256*(l+1)):
                t += D[m,n,o]
                x += A[m,n,o] * D[m,n,o]
                y += B[m,n,o] * D[m,n,o]
                z += C[m,n,o] * D[m,n,o]