Combining geometry and domain knowledge to interpret hand-drawn diagrams

One main challenge in building interpreters for hand-drawn sketches is the task of parsing a sketch to locate the individual symbols. Many existing pen-based systems avoid this problem by requiring the user to explicitly indicate the partitioning of the sketch with button clicks or pauses in drawing. We have created a parser that automatically locates symbols by looking for areas of high ink density, and for points at which the characteristics of the pen strokes change. To demonstrate our techniques, we have developed AC-SPARC, a sketch-based interface for the SPICE electric circuit analysis program. An evaluation of our interface has indicated that, even for novice users, our system can successfully locate and identify most of the circuit components in hand-drawn circuit diagrams.