Line connectivity algorithms for an asynchronous pyramid computer

Line tracing, which has been conjectured to play an important role in the visual perception of connectivity relations, is examined in this paper from the computational point of view. The problem is formulated in terms of pixel connectivity, with thin black lines on a white background serving as input. The complexity of line tracing is discussed relative to several computation models. Two algorithms for a MIMD pyramid with running time better than linear in the line length are presented and analyzed. Their performance is discussed in view of the available psychophysical results, and compared to that of several previously published algorithms. 9 1987 Academic Press, Inc.