A Simple Approach to Recognise Geometric Shapes Interactively

Abstract

This paper presents a simple method to recognise multistroke sketches of geometric shapes. It uses temporal adjacency and global geometric properties of figures to recognise a simple vocabulary of geometric shapes including solid and dashed line styles, selection and delete gestures. The geometric features used (convex hull, smallest-area regular polygons, perimeter and area scalar ratios) are invariant with rotation and scale of figures. We have found the method very usable with acceptable recognition rates although the multi-stroke approach poses problems in choosing appropriate values for time-outs. Although we have privileged simplicity over robustness, the method has proved suitable for interactive applications.