Edge Detection in Simple Scenes Using a Priori Information

A system of programs is described for the detection of the straight edge lines in simple scenes. Distinct lines are detected by a procedure that is relatively inexpensive. The more subtle lines are then located by a search that is much more costly per unit area, but which is only applied to certain areas suggested by the locations of the lines already found. The considerable efficiency of this approach to edge detection is discussed both theoretically and in relation to the performance of the present system. The heuristics used in proposing possible subtle lines are described in detail. In addition, considerable attention is devoted to other aspects of the procedure such as: local edge-detection operators, vertex finding, and the extraction of lines from local evidence.