Abstract:

In order to apply rotation sensitive features and recognition methods for recognizing rotatable sketched symbols, it is essential to recognize its orientation. A TDHbased orientation recognition method is proposed for sketched symbols. Tangent directions of resample points are extracted, and a histogram feature is constructed to carry directional information of the symbol’s strokes. The rotation angle between an unknown input symbol and a template symbol can be estimated by matching their TDH rotationally, and the input symbol can be adjusted to align with the template one subsequently. With an experiment on a set of 52 sketched courseofaction symbols, the results show that the error of rotation angle recognized by our method is less than 5° for over 80% of the tested symbols, and the recognition speed meets the real time requirements.

Key words: sketched symbols;orientation recognition;tangent direction histogram(TDH)