Overtraced strokes to single line drawing: Preparation of sketch for 3D interpretation

This paper presents a novel method for interpreting overtraced strokes to single line drawing. The approach consists of three stages: preprocessing, stroke classification, strokes grouping and fitting. The preprocessing methods include stroke preprocessing and grouping preprocessing. The former discuss the polygonal approximation to represents the stroke and the latter proposes a method to evaluate whether the strokes should be grouped by time interval and distance interval of two adjacent strokes. It is followed by an innovative strokes grouping process that handles polylines and curves separately. This paper proposes a method for rapid fitting overtraced line using the characteristics of stroke recognition result. According to the position relation of strokes recognition result, the two polylines are divided into difference catalogs. The definitions of the rotation angle and the endpoint of generalized stroke of the non-closed conic curve are proposed in this paper. The grouped strokes are fitted with 2D geometry and a complete definition of the fitting geometry of grouped stroke with linetype is proposed. This paper develops a human-computer interface prototype system FSR using the proposed theory. The interface overcomes the limitation where only a single line drawing can be sketched out as in most existing sketching programs, meanwhile is more intuitive and easy to the user. The FRS system has been tested with a number of overtraced and non-overtraced strokes, and the test results show that the algorithm achieves a satisfactory interpretation.