Handwriting recognition system using substroke analysis

Abstract

A handwritten pattern and stroke recognition system recognizes an input pattern by comparing it to reference patterns. The input and reference patterns comprise at least one stroke, where a stroke is defined as the series of sample points from pen-down to pen-up. The system of the present invention compares the input and reference patterns stroke by stroke and thus, compares input strokes to reference strokes. The system includes a tangent and stable point extractor, a reference database and a stable-point-based classifier. The extracter determines tangents to at least some of the sample points of the input stroke and determines, which of the sample points between a beginning and end of the input stroke are stable points. The reference database stores tangents of sample points of the reference strokes and stable points of the reference strokes. The stable-point-based classifier divides each input stroke and each reference stroke into at least two substrokes wherein each substroke has at least one of the stable points at an end thereof. The classifier also generates stroke match values indicating the quality of the match between the input stroke and the reference strokes based on the comparison of substrokes of the input stroke with corresponding substrokes of the reference strokes. The classifier selects the reference stroke providing the best match to the input stroke in accordance with a matching criterion. Finally, the classifier selects the reference pattern whose strokes best match the strokes of the input pattern.