4-directional chain code 2 0 8-directional chain code 2 3 43 5 2 4 0 7 00 1 2 3 4 0 1 2 3 5 6 7 4-directional chain code 8-directional chain code 0 X Y 0 2 1 3 0 X Y 0 1 2 4 3 5 6 7