A 2-D HMM method for offline handwritten character recognition

  • Authors:
  • Hee-Seon Park;Bong-Kee Sin;Jongsub Moon;Seong-Whan Lee

  • Affiliations:
  • Samsung Electronics Co. Ltd., Seoul, Korea;Pukyong National Univ., Pusan, Korea;Korea Univ., Chungnam, Korea;Korea Univ., Chungnam, Korea

  • Venue:
  • Hidden Markov models
  • Year:
  • 2001

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Abstract

In this paper we consider a hidden Markov mesh random field (HMMRF) for character recognition. The model consists of a "hidden" Markov mesh random field (MMRF) and on overlying probabilistic observation function of the MMRF. Just like the 1-D HMM, the hidden layer is characterized by the initial and the transition probability distributions, and the ovservation layer is defined by distribution functions for vector-quantized (VQ) observations. The HMMRF-based method consists of two phases: decoding and training. The decoding and the training algorithms are developed using dynamic programming and maximum likelihood estimation methods. To accelerate the computation in both phases, we employed a look-ahead scheme based on maximum marginal a posteriori probability criterion for third-order HMMRF. Tested on a largetst-set handwritten Korean Hangul character database, the model showed a promising result: up to 87.2% recognition rate with 8 state HMMRF and 128 VQ levels.