LAREX

LAREX is a semi-automatic open-source tool for layout analysis on early printed books. It uses a rule based connected components approach which is very fast, easily comprehensible for the user and allows an intuitive manual correction if necessary. The PAGE XML format is used to support integration into existing OCR workflows. Evaluations showed that LAREX provides an efficient and flexible way to segment pages of early printed books.

Please feel free to visit the tool homepage. A short user manual is available here.

Table of Contents

• Installation
  • Docker
  • Linux
  • Windows
  • Mac OS X
• Usage
• Configuration
• Related Publications

Additional information about developing for LAREX see here

Installation

Docker

This guide uses Docker and allows a platform agnostic installation of LAREX

Production

• See: LAREX Docker

Development

• Configure development/build.sh, run cd development and sh build.sh

Linux

This guide uses Tomcat 8, Java 8 and Ubuntu (please adjust accordingly for your setup)

• Install required packages: apt-get install tomcat8 maven openjdk-8-jdk
• Clone Repository: git clone https://github.com/OCR4all/LAREX.git
• Compile: mvn clean install -f LAREX/pom.xml.
• Copy or link the created war file to Tomcat:
  • Copy cp LAREX/target/Larex.war /var/lib/tomcat8/webapps/Larex.war
  • Link: sudo ln -s $PWD/LAREX/target/Larex.war /var/lib/tomcat8/webapps/Larex.war
• Start Tomcat: systemctl start tomcat8
  • (Restart Tomcat via systemctl restart tomcat8)
  • (To start Tomcat automatically at system boot systemctl enable tomcat8)

Windows

This guide uses Eclipse to simplify the setup on Windows

• Install Eclipse IDE for Enterprise Java Developers from the official website
• Download Tomcat 8 or up from the official website
• Create a Tomcat server in eclipse:
  • Open Window -> Show View -> Other... -> Server -> Servers
  • Click prompt to add a new server, select Apache -> Tomcat <version> Server -> Next-> set your Tomcat installation directory -> Finish.
• Clone Repository:
  • File -> Import -> Git -> Projects from Git -> Clone URI -> Set URI: https://github.com/OCR4all/LAREX.git -> [✓] master -> Next > -> Next > -> Import as gernal project -> Finish
• Set as Maven Project:
• Import Project
  • Right click on Larex -> Configure -> Convert to Maven Project -> Finish
• Update maven project (if not updated automatically)
  • Rightclick on Larex -> Maven -> Update Project... -> OK
• Start Larex
  • Right click on Larex -> Run As -> Run on Server.

macOS

Note: LAREX is mainly developed on Linux so the macOS build introductions may be outdated from time to time. If this is the case, feel free to contact us This guide uses homebrew (please adjust accordingly for your setup).

• Install Homebrew (see https://brew.sh/) and run brew update.
• Install required packages:
  • brew cask install adoptopenjdk8
  • brew install tomcat git maven
• (Verify Tomcat installation):
  • brew services list tomcat should be listed in the output of this command
• Clone Repository:
  • git clone https://github.com/OCR4all/LAREX.git
• Compile:
  • run mvn clean install -f LAREX/pom.xml.
• Copy or link the created war file to Tomcat
  • Copy: cp LAREX/target/Larex.war /usr/local/Cellar/tomcat/[version]/libexec/webapps/Larex.war
  • Link: ln -s $PWD/LAREX/target/Larex.war /usr/local/Cellar/tomcat/[version]/libexec/webapps/Larex.war
• Start Tomcat:
  • brew services start tomcat
  • (Restart Tomcat via brew services restart tomcat)

Usage

Access in browser

Go to localhost:8080/Larex.

Using your own images and books

You can add your own books by copying them to src/webapp/resources/books

(Or an alternative direction set in the config file. See section Configuration for more information).

Book directories must have the following structure:

bookDir/
├── <book_name>/ 
│    ├── <page_name>.png 
│    └── <page_name>.xml
└── <book2_name>/
     └── …

More information

Detailed information about the usage of LAREX can be found in the OCR4all getting started guides.

See sections and chapters about Segmentation, Ground Truth Correction and Post Correction.

Configuration

LAREX contains a configuration file (src/webapp/WEB-INF/larex.properties) with a few settings that can be set before running the application.

bookpath

The setting bookpath sets the file path of the books folder.

e.g. bookpath=/home/user/books (Linux)

e.g. bookpath=C:\Users\user\Documents\books (Windows)

LAREX will load the books from this folder.

[default /src/main/webapp/resources/books]

localsave

The setting localsave tells the application how to handle results locally when saved.

Please note:
To work properly in local mode it's required that the Page@imageFilename-attribute matches the actual filename (apart from the extension). This label will be used for local storage.

<mode>=[bookpath|savedir|none]

bookpath: save the result in the bookpath

savedir: save the result in a defined savedir

none: do not save the result locally [default]

e.g. localsave:bookpath

savedir

The setting savedir is needed if localsave mode is set to "savedir".

e.g. savedir=/home/user/save (Linux)

e.g. savedir=C:\Users\user\Documents\save (Windows)

websave

The setting websave tells the application how to handle results on the browser side when saved.

<value>=[true|false]

true: download the result after saving [default]

false: no action after saving

e.g. websave=true

modes

Set the accessible modes in the LAREX GUI <value>=[[segment][edit][lines][text]] A combination of the modes "segment", "edit", "lines" and "text" can be set as a space separated string. e.g. modes=segment lines

The order of those modes in the string also determines which mode is opened on startup, with the first in the list being opened as main mode. The mode "segment" can be replaced with "edit" in order to hide all auto segmentation features. ("edit" will be ignored if both are present)

[Default] modes=segment lines text

directrequest

This setting enables or disables the direct open feature.

<value>=[enable|disable]

This feature allows users to load a book from everywhere on the servers drive as well as to alter the options websave, localsave and savedir.

enable: enable direct request

disable: disable direct request [default]

e.g. directrequest=enable

This feature should be used with caution but is very useful when using LAREX in a workflow with other web applications. (e.g. in Docker)

The easiest direct request would be via a html form with the values bookpath, bookname, websave (optional), localsave (optional) and savedir (optional).

<form action="http://localhost:8080/Larex/direct" method="POST">
	bookpath: <input type="text" name="bookpath"/><br>
	bookname: <input type="text" name="bookname"/><br>
	websave: <input type="text" name="websave"/><br>
	localsave: <input type="text" name="localsave"/><br>
	savedir: <input type="text" name="savedir"/><br>
	modes: <input type="text" name="modes"/><br>
	<input type="submit"/>
</form>

OCR4all UI mode

This setting enables or disables OCR4all UI mode.

<value>=[enable|disable]

This setting allows displaying and/or hiding certain UI elements when LAREX is used in combination with OCR4all.

enable: enable OCR4all UI mode

disable: disable OCR4all UI mode [default]

e.g. ocr4all=enable

Citing LAREX

If you are using LAREX please cite:

Reul, C., Springmann, U., Puppe, F.: Larex: A semi-automatic open-source tool for layout analysis and region extraction on early printed books Proceedings of the 2nd International Conference on Digital Access to Textual Cultural Heritage (2017)

@inproceedings{reul2017larex,
  title={Larex: A semi-automatic open-source tool for layout analysis and region extraction on early printed books},
  author={Reul, Christian and Springmann, Uwe and Puppe, Frank},
  booktitle={Proceedings of the 2nd International Conference on Digital Access to Textual Cultural Heritage},
  pages={137--142},
  year={2017}
}