Handwritten Numeral String Recognition: Effects of Character Normalization and Feature Extraction

Cheng-Lin LIU
Hiroshi SAKO
Hiromichi FUJISAWA

Publication
IEICE TRANSACTIONS on Information and Systems   Vol.E88-D    No.8    pp.1791-1798
Publication Date: 2005/08/01
Online ISSN: 
DOI: 10.1093/ietisy/e88-d.8.1791
Print ISSN: 0916-8532
Type of Manuscript: Special Section PAPER (Special Section on Document Image Understanding and Digital Documents)
Category: String Recognition
Keyword: 
numeral string recognition,  integrated segmentation and recognition,  normalization,  aspect ratio function,  feature extraction,  slant correction,  

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Summary: 
The performance of integrated segmentation and recognition of handwritten numeral strings relies on the classification accuracy and the non-character resistance of the underlying character classifier, which is variable depending on the techniques of pattern normalization, feature extraction, and classifier structure. In this paper, we evaluate the effects of 12 normalization functions and four selected feature types on numeral string recognition. Slant correction (deslant) is combined with the normalization functions and features so as to create 96 feature vectors, which are classified using two classifier structures. In experiments on numeral string images of the NIST Special Database 19, the classifiers have yielded very high string recognition accuracies. We show the superiority of moment normalization with adaptive aspect ratio mapping and the gradient direction feature, and observed that slant correction is beneficial to string recognition when combined with good normalization methods.


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