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Transformer for Handwritten Text Recognition Using Bidirectional Post-decoding

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Document Analysis and Recognition – ICDAR 2021 (ICDAR 2021)

Abstract

Most recently, Transformers – which are recurrent-free neural network architectures – achieved tremendous performances on various Natural Language Processing (NLP) tasks. Since Transformers represent a traditional Sequence-To-Sequence (S2S)-approach they can be used for several different tasks such as Handwritten Text Recognition (HTR). In this paper, we propose a bidirectional Transformer architecture for line-based HTR that is composed of a Convolutional Neural Network (CNN) for feature extraction and a Transformer-based encoder/decoder, whereby the decoding is performed in reading-order direction and reversed. A voter combines the two predicted sequences to obtain a single result. Our network performed worse compared to a traditional Connectionist Temporal Classification (CTC) approach on the IAM-dataset but reduced the state-of-the-art of Transformers-based approaches by about 25% without using additional data. On a significantly larger dataset, the proposed Transformer significantly outperformed our reference model by about 26%. In an error analysis, we show that the Transformer is able to learn a strong language model which explains why a larger training dataset is required to outperform traditional approaches and discuss why Transformers should be used with caution for HTR due to several shortcomings such as repetitions in the text.

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Notes

  1. 1.

    https://docs.python.org/3/library/difflib.html.

  2. 2.

    https://github.com/jpuigcerver/Laia/tree/master/egs/iam.

  3. 3.

    Note, this behaviour can easily produced, e.g., in Google-translate by translating repeated words (without line breaks). Translating 16 times the German word “Mann” results in 17 repetitions of the English translation “man” (as of 01/11/2021).

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Acknowledgments

This work was partially funded by the European Social Fund (ESF) and the Ministry of Education, Science and Culture of Mecklenburg-Western Pomerania (Germany) within the project Neural Extraction of Information, Structure and Symmetry in Images (NEISS) under grant no ESF/14-BM-A55-0006/19.

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Correspondence to Christoph Wick .

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Wick, C., Zöllner, J., Grüning, T. (2021). Transformer for Handwritten Text Recognition Using Bidirectional Post-decoding. In: Lladós, J., Lopresti, D., Uchida, S. (eds) Document Analysis and Recognition – ICDAR 2021. ICDAR 2021. Lecture Notes in Computer Science(), vol 12823. Springer, Cham. https://doi.org/10.1007/978-3-030-86334-0_8

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  • DOI: https://doi.org/10.1007/978-3-030-86334-0_8

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