OCR-D Browser

An extensible viewer for OCR-D mets.xml files

• Screenshot
• Features
• Installation
  • Native
    • From source
    • Via pip
  • Docker
• Usage
  • Native GUI
  • Docker service
• Configuration
  • Configuration file locations
  • Configuration file syntax

Screenshot

Features

• Browse fileGrps and pages, arranging views next to each other for comparison
• PageView: Show original or derived page images with PAGE-XML annotations overlay, similar to PageViewer
• ImageView: Show original or derived images (AlternativeImage on any level of the structural hierarchy)
• ImageView: Show multiple images at once for different pages (horizontally) or different segments (vertically), zooming freely
• XmlView: Show raw PAGE-XML with syntax highlighting, open with PageViewer
• TextView: Show concatenated PAGE-XML text annotation
• DiffView: Show a simple diff comparison between text annotations from different fileGrps
• HtmlView: Show rendered HTML comparison from dinglehopper evaluations

Installation

OCR-D Browser requires Python 3.7 or higher.

Native (tested on Ubuntu 18.04/20.04)

The native installation requires GTK 3.

In any case you need a virtual environment with a current pip version (>=20), preferably your existing OCR-D venv:

Create a current pip venv:

sudo apt install python3-pip python3-venv 
python3 -m venv venv
source venv/bin/activate
pip install --upgrade pip setuptools wheel

From source

git clone https://github.com/hnesk/browse-ocrd.git 
cd browse-ocrd
sudo make deps-ubuntu
make install

Via pip

sudo apt install libcairo2-dev libgirepository1.0-dev
pip install browse-ocrd

Docker

If you have installed Docker, you can build OCR-D Browser as a web service:

docker build -t ocrd_browser .

Or use a prebuilt image from Dockerhub:

docker pull hnesk/ocrd_browser

Usage

Native GUI

Start the app with the filesystem path to the METS file of your OCR-D workspace:

browse-ocrd ./path/to/mets.xml

You can still open another METS file from the UI though.

Docker service

When running the webservice, you need to pass a directory DATADIR which (recursively) contains all the workspaces you want to serve. The top entrypoint http://localhost/ will show an index page with a link http://localhost/browse/... for each workspace path. Each link will run browse-ocrd at that workspace in the background, and then redirect your browser to the internal Broadway server, which renders the app in the web browser.

To start up, just do:

docker run -it --rm -v DATADIR:/data -p 8085:8085 -p 8080:8080 ocrd_browser

Configuration

Configuration file locations

At startup the following directories a searched for a config file named ocrd-browser.conf

# directories and their default values under Ubuntu 20.04
GLib.get_system_config_dirs()  # '/etc/xdg/xdg-ubuntu/ocrd-browser.conf', '/etc/xdg/ocrd-browser.conf'
GLib.get_user_config_dir()     # '/home/jk/.config/ocrd-browser.conf'  
os.getcwd()                    # './ocrd-browser.conf'

Configuration file syntax

The ocrd-browser.conf file is an ini-file with the following sections and keys:

[FileGroups]
# Preferred fileGrp names for thumbnail display in the Page Browser 
# Comma separated list of regular expressions
preferredImages = OCR-D-IMG, OCR-D-IMG.*, ORIGINAL

# Each Tool has a section header [Tool XYZ]
# At the moment the only defined tool is "PageViewer"  
[Tool PageViewer]
# shell commandline to execute with placeholders  
commandline = /usr/bin/java -jar /home/jk/bin/JPageViewer/JPageViewer.jar --resolve-dir {workspace.directory} {file.path.absolute}

Note: You can get PRImA's PageViewer at Github.

The commandline string will be used as a python format string with the keyword arguments:

• workspace : The current ocrd.Workspace, all properties get shell escaped (by shlex.quote) automatically.
• file : The current ocrd_models.OcrdFile, all properties get shell escaped (by shlex.quote) automatically, also there is an additional property path with the properties absolute and relative, so {file.path.absolute} will be replaced by the shell quoted absolute path of the file.

Configuration by environment variables

It is possible to set or override values of the configuration through environment variables. The environment variables follow this structure : BROCRD__{SECTION}__{KEY}, where SECTION and KEY are in upper snake case and divided by a double underscore (__). If the section title contains spaces, the single words are also divided by __.

Some examples:

BROCRD__FILE_GROUPS__PREFERRED_IMAGES='THUMB'  
BROCRD__TOOL__PAGEVIEWER__COMMANDLINE='ls {file.path.absolute}'