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Levenshtein OCR (2209.03594v2)

Published 8 Sep 2022 in cs.CV

Abstract: A novel scene text recognizer based on Vision-Language Transformer (VLT) is presented. Inspired by Levenshtein Transformer in the area of NLP, the proposed method (named Levenshtein OCR, and LevOCR for short) explores an alternative way for automatically transcribing textual content from cropped natural images. Specifically, we cast the problem of scene text recognition as an iterative sequence refinement process. The initial prediction sequence produced by a pure vision model is encoded and fed into a cross-modal transformer to interact and fuse with the visual features, to progressively approximate the ground truth. The refinement process is accomplished via two basic character-level operations: deletion and insertion, which are learned with imitation learning and allow for parallel decoding, dynamic length change and good interpretability. The quantitative experiments clearly demonstrate that LevOCR achieves state-of-the-art performances on standard benchmarks and the qualitative analyses verify the effectiveness and advantage of the proposed LevOCR algorithm. Code is available at https://github.com/AlibabaResearch/AdvancedLiterateMachinery/tree/main/OCR/LevOCR.

Citations (27)

Summary

  • The paper introduces an iterative recognition paradigm leveraging deletion and insertion operations to dynamically refine scene text predictions.
  • The method fuses robust visual features from a modified ResNet with a transformer-based linguistic module, enabling cross-modal interaction without explicit alignment.
  • Numerical results on benchmarks like IC13, SVT, and IIIT demonstrate LevOCR’s state-of-the-art accuracy and enhanced interpretability in complex scenarios.

An Overview of "Levenshtein OCR"

This paper introduces LevOCR, an innovative scene text recognition method leveraging a Vision-Language Transformer (VLT) inspired by the Levenshtein Transformer (LevT) from NLP. The authors propose a paradigm where text recognition is approached as an iterative sequence refinement task. Utilizing operations like deletion and insertion, LevOCR enables dynamic length adjustments and enhances interpretability, distinguishing itself from standard sequence recognition approaches.

Methodological Insights

LevOCR integrates components such as Visual Feature Extraction (VFE) and Linguistic Context (LC), culminating in a Vision-Language Transformer (VLT) architecture. The VFE employs a modified ResNet backbone to extract robust visual features, whereas the LC involves a transformer-based textual module for linguistic information synthesis. By merging these modalities in the VLT, LevOCR effectively facilitates cross-modal information interaction, circumventing the need for explicit alignments.

The methodology is underpinned by imitation learning, fostering a flexible and adaptable prediction process. LevOCR's iterative nature, informed by Levenshtein's principles, allows it to refine predictions by iterating over deletion and insertion actions—a strategy that enhances both flexibility and interpretability.

Numerical and Qualitative Analysis

Quantitatively, the LevOCR achieves state-of-the-art results across well-established scene text benchmarks such as IC13, SVT, and IIIT. The paper reports significant improvements over previous methodologies, with notable accuracy leaps attributed to the effective synthesis of visual and linguistic data.

Qualitatively, examples provided in the text highlight LevOCR's capability to navigate complex scenarios, such as occluded or distorted text, by leveraging both modalities. The interpretability of its operations allows users to discern the rationale behind specific deletions and insertions, thus increasing the transparency of decisions made during the text recognition process.

Theoretical and Practical Implications

Theoretically, LevOCR contributes to the broader discourse on cross-modal learning and sequence refinement. By demonstrating the applicability of NLP-inspired techniques in visual tasks, the authors open avenues for further exploration in synergizing vision and LLMs. Practically, LevOCR's iterative and interpretable approach could enhance applications like traffic sign recognition and content-based retrieval, where accuracy and understanding of algorithmic decisions are pivotal.

Future Directions

Future research could explore optimizing the computation time associated with LevOCR's iterative refinement process. Given the architecture’s current latency, developing more efficient alternatives while maintaining or enhancing interpretability would be vital. Additionally, extending the approach to encompass more complex text patterns and languages could broaden the applicability of LevOCR.

In conclusion, this paper presents LevOCR as a significant advancement in scene text recognition, combining the strengths of vision and language modalities with a focus on interpretability and flexibility. While the current results are promising, further work could unlock even more potential for this approach in both theoretical and real-world applications.

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