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I have always found OCR technology to be behind on open source systems. I've also watched the Ocropus project since its infancy. I've tried what I've heard is the best OCR engine available for Linux, Tesseract, and have found it woefully lacking for business documents. Are there any other more promising OCR implementations? What about the even more hopeful goal for interpreting handwriting? What is possible on *nix systems in this field?

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5 Answers 5

I found a similar question over on StackOverflow and the Asprise OCR SDK, one of the linked commercial products, boasts a Linux version.

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... OCR is more than "only character recognition". Image handling, preprocessing - page/layout analysis to find the texts, images, tables or barcodes. For the recognition, you have to deal with different fonts, sizes and languages. This is important because to get good results you have to use dictionaries and language definitions. Finally people expect more export options than text (e.g., XML, RTF, or searchable PDF). There are some commercial options for SDKs, but they are not cheap and for free.

Recently I found a CLI OCR for Linux from ABBYY. There is a free 100 page trial.

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Well, depends what you mean by 'business documents'.

Cuneiform

I tested cuneiform with some business letters and I was quite astonished by its low error rate (regarding mis-recognized characters or words).

For my use case I only need the raw text for indexing purposes - I am not interested in text to layout element mapping or something like that.

And the documents are just one column.

Unfortunately, cuneiform currently (as of 1.1) has some problems:

You can disable the layout algorithm like this:

$ cuneiform --singlecolumn -l ger -f text -o foo.txt imgfile

(-l specifies the language of the source document)

Tesseract

Can't really test it because it directly segfaults (using Ubuntu 11.10 packages - i.e. Tesseract 2.04):

$ tesseract image-0001.tif foo -l deu
Tesseract Open Source OCR Engine
index < len:Error:Assert failed:in file ../ccstruct/rejctmap.h, line 240
zsh: segmentation fault

Hardware

Sane has very good support for a lot of automated document feed (ADF) scanners, e.g. for Avision and Fujitsu ones.

Included with Sane is the scanadf command line program which you can use to build scripted scan pipelines.

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I tried Cuneiform. It works well if you need to recognize scanned image (not photos). I used Yagf as a GUI. –  Sergei Oct 13 '12 at 9:58

If you have a budget, I strongly recommend ABBYY FineReader Engine CLI for Linux. Our company has been using it in our web-application for a year and we plan to renew the license. Very good recognition quality, command-line interface, recognition in many languages.

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There are few popular OCR command-line tools:

  • Tesseract (ReadMe, FAQ) (Python)

    Also available for: Tesseract .NET, Tesseract iOS

    An OCR Engine that was developed at HP Labs between 1985 and 1995... and now at Google. Tesseract is probably the most accurate open source OCR engine available.

    Usage:

    tesseract [inputFile] [outputFile] [-l optionalLanguageFile] [PathTohOCRConfigFile]
    
  • GOCR

    Open-source character recognition. It converts scanned images of text back to text files. GOCR can be used with different front-ends, which makes it very easy to port to different OSes and architectures. It can open many different image formats, and its quality have been improving in a daily basis.

  • OCRopus™ (FAQ) (written in Python, NumPy, and SciPy)

    OCR system focusing on the use of large scale machine learning for addressing problems in document analysis, featuring pluggable layout analysis, pluggable character recognition, statistical natural language modeling, and multi-lingual capabilities.

    The OCRopus engine is based on two research projects: a high-performance handwriting recognizer developed in the mid-90's and deployed by the US Census bureau, and novel high-performance layout analysis methods.

    OCRopus is development is sponsored by Google and is initially intended for high-throughput, high-volume document conversion efforts. We expect that it will also be an excellent OCR system for many other applications.

  • Tessnet2 (Open source, OCR, Tesseract, .NET, DOTNET, C#, VB.NET, C++/CLI)

    Tesseract is a C++ open source OCR engine. Tessnet2 is .NET assembly that expose very simple methods to do OCR. Tessnet2 is under Apache 2 license (like tesseract), meaning you can use it like you want, included in commercial products.

Other already suggested: ABBYY CLI OCR for Linux, Asprise OCR

For more complete list, check: List of optical character recognition software at Wikipedia

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