= Tesseract
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{c}
<Tesseract (software)> is an open-source engine for <optical character recognition>. It combines image analysis with trained recognition data to extract text from images. Its documentation describes a command-line interface and a programming interface, with recognition data for different writing systems. A language choice affects the model used; it does not translate the recognized text.<Tesseract User Manual by the Tesseract project>[Introduction and Usage; Command Line Usage, Using One Language]{ref}
For example, the documented command `tesseract scan.png result -l eng` reads an image, selects English recognition data and writes text to `result.txt`. The output basename is `result`, so the filename extension is supplied by the selected output format. Adding `pdf` requests a PDF containing the page image and a searchable text layer. If recognition confuses a letter in the image, searching that text layer can still miss the intended word.<Tesseract User Manual by the Tesseract project>[Command Line Usage, Simplest Invocation, Using One Language and Searchable pdf output]{ref}
The architecture has changed over its history. <Ray Smith (OCR researcher)>'s 2007 paper describes an engine that groups connected image outlines into lines and words, then recognizes them in successive passes. Version 4 introduced recognition based on <long short-term memory> <neural networks>; the 5.x manual documents this engine alongside the legacy option.<An Overview of the Tesseract OCR Engine by Ray Smith>[§2, printed p. 629, architecture and recognition passes]{ref}<Tesseract User Manual by the Tesseract project>[Tesseract with LSTM; Command Line Usage, Available OCR Engines in Tesseract 5]{ref}
A useful test compares output with a checked transcription using <character error rate>, while also inspecting omitted regions and reading order. Recognition accuracy depends on image quality, layout and matching language data. Installing the engine alone does not establish the accuracy of a particular scanned collection.
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