Processing of Off-Line Handwritten Text: Polygonal Approximation and Enforcement of Temporal Information

Algorithms to process off-line Arabic handwriting prior to recognition are presented. The first algorithm converts smoothed and thinned images into polygonal approximations. The second algorithm determines the start vertex of writing. The third algorithm enforces temporal information by traversing the graph of the stroke in an order consistent with Arabic handwriting. It implements the following heuristic rule: the minimum distance path that traverses the stroke′s polygon from the start vertex to the end vertex has its vertices ordered as they were generated when the stroke was written. This third algorithm is developed from a standard solution of the Chinese postman′s problem applied to the graph of the stroke. Special rules to enforce temporal information on the stroke to obtain the most likely traversal that is consistent with Arabic handwriting are applied. Unconstrained handwritten strokes written by five subjects, (n = 4065) were used in testing. In 92.6% of the samples, the proposed algorithms restored the actual temporal information.