GNU Ocrad vs Tesseract OCR

GNU Ocrad is a free OCR program and library for Linux and self-hosted use. It reads PNG and PNM images and produces recognized text as 8-bit bytes or UTF-8. Its layout analyzer can separate columns and text blocks on printed pages. Ocrad runs as a standalone console application or as a backend for other programs. Documented options cover image transformations, layout detection, character recognition, text filters, and an OCR results file containing structured recognition details. The software uses ISO 10646 internally, with character-set selection through the --charset option. The manual recommends characters at least 20 pixels high and says 300 dpi scanning usually reaches a suitable size. It also notes sensitivity to character defects and difficulty adding recognition for new characters. The project describes Ocrad mainly as a research project, with algorithms that may change in later releases. Latest releases are available through GNU mirrors, while older and testing versions are hosted on Savannah.

Tesseract OCR is a free, open-source OCR engine and command-line program for extracting printed text from images. It accepts image inputs including PNG, JPEG, and TIFF, and can output plain text, hOCR, PDF, TSV, ALTO, and PAGE formats. PDF options include searchable PDFs and invisible-text-only PDFs. Tesseract 4 and later include an LSTM-based engine focused on line recognition, while Legacy OCR Engine mode retains compatibility with Tesseract 3. The project says it recognizes more than 100 languages out of the box; language data is installed separately from the engine. Developers can build applications with the C or C++ libtesseract API, and the documentation lists wrappers for other languages. The repository code uses the Apache License 2.0. Tesseract does not include a graphical user interface and points users to third-party interfaces. It uses Leptonica to open images, and improving input image quality may be needed for better recognition results. Installation instructions cover Linux, macOS, and Windows, with listed platforms also including Android and self-hosting.