I. Executive Summary:
Optical Character Recognition (OCR) on low-quality PDF documents poses significant challenges due to noise, blur, and low resolution. This report analyzes various OCR applications and libraries in Rust, Python, and as command-line tools for such documents. While traditional engines like Tesseract need substantial preprocessing, deep learning-based solutions like EasyOCR and docTR in Python show promise. OCRmyPDF, a Python tool leveraging Tesseract with image processing and optimization, is also a strong contender. The report details performance, accuracy claims, and usability, offering recommendations for optimizing OCR on degraded PDFs.
II. Introduction:
Optical Character Recognition (OCR) is vital for extracting text from images, scanned documents, and PDFs into machine-readable text, crucial for archiving, automation, and analysis. Low-quality PDFs present obstacles like noise, blur, low resolution, skewing, and compression artifacts [1]. Older documents (e.g., newspapers) with small fonts, dense columns, and background clutter are particularly challenging [1]. Manual correction of errors from standard OCR can be more time-consuming than retyping [1]. Layout complexities, such as newspaper column separators, can confuse OCR engines [1]. The initial scan quality is key to OCR accuracy, and post-processing has limited effectiveness on severely degraded inputs [2]. Solutions are needed that are accurate, fast, and can handle degradation in low-quality PDFs. This report compares high-performance OCR options in Rust, Python, and as command-line applications.
III. Rust-Based OCR Solutions:
A. ocrs:
ocrs is a new, open-source OCR engine in Rust, emphasizing user-friendliness and cross-platform compatibility [21]. It aims for accurate text extraction from various images with minimal preprocessing using machine learning [21]. Currently in early preview, it primarily supports the Latin alphabet (e.g., English) [21], with plans for more languages [21]. Its architecture uses neural networks trained with PyTorch, exported to ONNX, and run with the RTen inference engine [21]. Available as a Rust library and a CLI tool [21], the CLI offers basic OCR, JSON output with layout, and image annotation [21]. Building in release mode is crucial for performance [23]. While promising due to its ML approach, its early stage and limited language support might restrict its immediate use for all low-quality PDFs, especially those with non-Latin scripts [21]. Further performance evaluation on diverse low-quality PDFs is needed.