Fix for Bug #3633: do away with "quads [2][3] = 255;" The four lowest bits in each quads[i][j] correspond to the 2x2 binary patterns Q_1, Q_2, Q_3 in the NM paper [1] (see in page 4 at the end of first column). Q_1 and Q_2 have four patterns, while Q_3 has only two.