Grouping of Multiple Overtraced Strokes in Interactive Freehand Sketches

This paper presents a method that groups multiple over traced pen strokes for converting online multiple over tracing sketches into line drawings. Firstly, tolerance zones around strokes are built during stroke preprocessing. Secondly, users inputs are divided into stroke groups by a grouping procedure, which relies on a over tracing judgment algorithom that uses the percentage of the sampling points of the smaller stroke which fall into the other's tolerance zone to determine whether two strokes should be grouped together. Finally, the stroke groups are fitted with 2D geometric primitives including lines, ellipses and arcs. The proposed method is proved to be robust and achieves a satisfactory interpretative efficiency.