Handwritten digit recognition by hierarchical displacement extraction with gradual prototype elimination

This paper investigates the performance of a handwritten character recognition method by hierarchical displacement extraction based on NIST special database (HSF7). The method is composed of a displacement extraction technique and a coarse-to-fine search strategy. In the displacement extraction technique, the displacement (correspondence) between an input pattern and a prototype is iteratively computed by minimizing a functional defined in the framework of regularization theory. In the coarse-to-fine search strategy, the above-mentioned displacement is determined with multiresolution images so as to avoid the pitfalls of local minimum and make the number of iterations low. In addition, a new idea is proposed for reducing the cost of computation without degrading the recognition performance, in which the number of candidate prototypes is eliminated gradually through the hierarchical procedure of the coarse-to-fine search strategy