“…By adding the masks in the Figures 1 and 6, results 14 masks in total, but the last ones can be combined with P 1 , P 2 by means of Boolean operations in order to obtain the masks shown in the Figure 7. Also, A 1 , A 2 , A 3 , A 4 , A 5 , A 6 , A 7 and A 8 , are particular cases of B 1 , B 2 , B 3 y B 4 ; furthermore, if the pixel opposed to the one labeled 1 has value 1 in the masks P 3 , P 4 , P 5 and P 6 , the results are also particular cases of B 1 , B 2 , B 3 , B 4 . These masks include all the possible configurations of end points.…”