Enhancement of text recognition for hanja handwritten documents of Ancient Korea

TL;DR

This paper presents a high-performance OCR model for ancient Korean hanja handwritten documents, utilizing data augmentation and a two-stage detection approach to achieve 90% recognition accuracy on cursive scripts.

Contribution

The study introduces a novel OCR method combining data augmentation and HRNet for recognizing complex hanja handwritten texts, addressing unique stylistic and historical challenges.

Findings

Achieved 90% recognition accuracy on cursive hanja documents.

Data augmentation with variable cropping improves OCR performance.

Performance is influenced by character variants and stylistic features.

Abstract

We implemented a high-performance optical character recognition model for classical handwritten documents using data augmentation with highly variable cropping within the document region. Optical character recognition in handwritten documents, especially classical documents, has been a challenging topic in many countries and research organizations due to its difficulty. Although many researchers have conducted research on this topic, the quality of classical texts over time and the unique stylistic characteristics of various authors have made it difficult, and it is clear that the recognition of hanja handwritten documents is a meaningful and special challenge, especially since hanja, which has been developed by reflecting the vocabulary, semantic, and syntactic features of the Joseon Dynasty, is different from classical Chinese characters. To study this challenge, we used 1100 cursive documents, which are small in size, and augmented 100 documents per document by cropping a randomly sized region within each document for training, and trained them using a two-stage object detection model, High resolution neural network (HRNet), and applied the resulting model to achieve a high inference recognition rate of 90% for cursive documents. Through this study, we also confirmed that the performance of OCR is affected by the simplified characters, variants, variant characters, common characters, and alternators of Chinese characters that are difficult to see in other studies, and we propose that the results of this study can be applied to optical character recognition of modern documents in multiple languages as well as other typefaces in classical documents.