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Mathematical Problems in Engineering
Volume 2015 (2015), Article ID 536192, 12 pages
Research Article

An Efficient Primitive-Based Method to Recognize Online Sketched Symbols with Autocompletion

1Equipment Academy, Beijing 101416, China
2Department of Information Systems, Academy of National Defense Information, Wuhan 430010, China

Received 21 January 2015; Revised 27 March 2015; Accepted 9 April 2015

Academic Editor: Nazrul Islam

Copyright © 2015 Wei Deng et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We present a new structural method of sketched symbol recognition, which aims to recognize a hand-drawn symbol before it is fully completed. It is invariant to scale, stroke number, and order. We also present two novel descriptors to represent the spatial distribution between two primitives. One is invariant to rotation and the other is not. Then a symbol is represented as a set of descriptors. The distance between the input symbol and the template one is calculated based on the assignment problem. Moreover, a fast nearest neighbor (NN) search algorithm is proposed for recognition. The method achieves a satisfactory recognition rate in real time.