This paper shows how mathematical morphological operators can be applied to computer go. On the one hand, mathematical morphology is a very powerful tool within image processing community. On the other hand, the Zobrist's model is well known within the computer go community for its "influence" recognition. We present a model, derived from the closing operator of mathematical morphology and from the Zobrist's model, which yields very good results for "territory" recognition. Moreover, we give efficient implementations of the dilation operator and territory recognition for computer go. This model was found when developing Indigo, our go playing program, and is now used with success in GnuGo, the go playing program of the Flee Software Foundation.
