Linux Apps Tutorials - Herong's Tutorial Examples - v1.02, by Herong Yang
Install Tesseract as the OCR Engine
This section provides a tutorial example on how to install Tesseract as the OCR Engine.
What Is Tesseract? Tesseract is an open source OCR (Optical Character Recognition) engine and command line program.
Tesseract was originally developed at Hewlett-Packard Laboratories Bristol and at Hewlett-Packard Co, Greeley Colorado between 1985 and 1994, with some more changes made in 1996 to port to Windows, and some C++izing in 1998. In 2005 Tesseract was open sourced by HP. Since 2006 it is developed by Google.
Here is what I did to install Tesseract on my CentOS computer.
1. Search for "tesseract" package information. It seems to be in the EPEL repository:
herong$ sudo dnf info tesseract
Extra Packages for Enterprise Linux 8 - x86_64
Available Packages
Name : tesseract
Version : 4.1.0
Release : 1.el8
Architecture : x86_64
Size : 1.4 M
Source : tesseract-4.1.0-1.el8.src.rpm
Repository : epel
Summary : Raw OCR Engine
URL : https://github.com/tesseract-ocr/tesseract
License : ASL 2.0
Description : A commercial quality OCR engine originally developed
: at HP between 1985 and 1995. In 1995, this engine was
: among the top 3 evaluated by UNLV. It was open-sourced
: by HP and UNLV in 2005.
2. Try to install it. It seems to require a missing library, "liblept.so".
herong$ sudo dnf install tesseract
Error:
Problem: conflicting requests
- nothing provides liblept.so.5()(64bit) needed
by tesseract-4.1.0-1.el8.x86_64
3. Search "liblept.so" on the Internet. I found that liblept.so is the library created from the Leptonica package.
4. Search for "Leptonica" package. I found it in the "PowerTools" package repository:
herong$ sudo dnf --enablerepo=PowerTools install leptonica
Installed:
leptonica-1.76.0-2.el8.x86_64
5. Install Tesseract again. It seems to require a missing library, "liblept.so".
herong$ sudo dnf install tesseract
Installed:
tesseract-4.1.0-1.el8.x86_64
tesseract-langpack-eng-4.0.0-6.el8.noarch
tesseract-tessdata-doc-4.0.0-6.el8.noarch
Complete!
6. Test the "tesseract" command:
herong$ tesseract --help
Usage:
tesseract --help | --help-extra | --version
tesseract --list-langs
tesseract imagename outputbase [options...] [configfile...]
OCR options:
-l LANG[+LANG] Specify language(s) used for OCR.
NOTE: These options must occur before any configfile.
Single options:
--help Show this help message.
--help-extra Show extra help for advanced users.
--version Show version information.
--list-langs List available languages for tesseract engine.
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