Finding perceptually closed paths in sketches and drawings
Closed or nearly closed regions are an important form of perceptual structure arisng both in natural imagery and in many forms of human-created imagery including sketches, line art, graphics and formal drawings. This paper presents an effective algorithm especially suited for finding perceptually salient, compact closed region structure in hand-drawn sketches and line art. ...
Saund, E. Finding perceptually closed paths in sketches and drawings. IEEE Transactions on Pattern Analysis and Machine Intelligence. 2003 April; 25 (4): 475-491.