Early Sketch Processing with Application in HMM Based Sketch Recognition

Freehand sketching is a natural and crucial part of everyday human interaction, yet is almost totally unsupported by current user interfaces. With the increasing availability of tablet notebooks and pen based PDAs, sketch based interaction has gained attention as a natural interaction modality. We are working to combine the flexibility and ease of use of paper and pencil with the processing power of a computer, to produce a user interface for design that feels as natural as paper, yet is considerably smarter. One of the most basic tasks in accomplishing this is converting the original digitized pen strokes in a sketch into the intended geometric objects. In this paper we describe an implemented system that combines multiple sources of knowledge to provide robust early processing for freehand sketching. We also show how this early processing system can be used as part of a fast sketch recognition system with polynomial time segmentation and recognition algorithms.