A Blended Attention-CTC Network Architecture for Amharic Text-image Recognition

Abstract

In this paper, we propose a blended Attention-Connectionist Temporal Classification (CTC) network architecture for a unique script, Amharic, text-image recognition. Amharic is an indigenous Ethiopic script that uses 34 consonant characters with their 7 vowel variants of each and 50 labialized characters which are derived, with a small change, from the 34 consonant characters. The change involves modifying the structure of these characters by adding a straight line, or shortening and/or elongating one of its main legs including the addition of small diacritics to the right, left, top or bottom of the character. Such a small change affects orthographic identities of character and results in shape similarly among characters which are interesting, but challenging task, for OCR research. Motivated with the recent success of attention mechanism on neural machine translation tasks, we propose an attention-based CTC approach which is designed by blending attention mechanism directly within the CTC network. The proposed model consists of an encoder module, attention module and transcription module in a unified framework. The efficacy of the proposed model on the Amharic language shows that attention mechanism allows learning powerful representations by integrating information from different time steps. Our method outperforms state-of-the-art methods and achieves 1.04% and 0.93% of the character error rate on ADOCR test datasets.