Combined with the Leptonica Image Processing Library Tesseract can read a wide variety of image formats and convert them to text in over 40 languages.
This code is a raw OCR engine. It has no output formatting and no UI. It can detect fixed pitch vs proportional text. Nevertheless in 1995 this engine was in the top 3 in terms of character accuracy, and it compiles and runs on both Linux and Windows. Training code is included in the open source release.
The core developer on the project is Ray Smith (theraysmith).
Thomas Breuel (tmbdev) and Ilya Mezhirov (mezhirov) work on the OCRopus project, for which Tesseract is one of the pluggable OCR engines; OCRopus also provides layout analysis and statistical language modeling.
Most of the work on Tesseract is sponsored by Google.