“…In the literature, a variety of formal models to recognize or generate two-dimensional arrays of symbols, called pictures, have been proposed [3,13,17,21,31], and further properties of string languages have been formulated for two dimensions [4][5][6]19,23,24,33]. This research was motivated by problems arising from the area of image processing and pattern recognition [10,28], and also plays a role in frameworks concerning cellular automata and other models of parallel computing [22,32].…”