Judging and Grouping Methods for Online Overtraced Freehand Sketch

This paper describes a method for grouping and fitting online overtraced strokes to 2D geometric primitives, which are further interpreted as 2D line drawings. Whether two strokes are overtraced is judged by the number of the sampling points of the stroke with smaller minimum bounding rectangle, which fall into the other’s tolerance zone. The grouping method does not rely on the stroke classification and can group different types of strokes together. It divides all strokes in the sketch into a set of stroke groups, which are finally fitted with geometric primitives such as straight lines, polylines and conic curves. This paper develops a human-computer interface prototype system FSR_DJ using the proposed theory, which has been tested with a number of overtraced sketches and the test results show that the algorithm achieves a satisfactory interpretative efficiency.