OCR-D/core

Python modules implementing OCR-D specs and related tools

• Introduction
• Installation
• Command line tools
  • ocrd CLI
  • ocrd-dummy CLI
• Configuration
• Packages
  • ocrd_utils
  • ocrd_models
  • ocrd_modelfactory
  • ocrd_validators
  • ocrd
• bash library
  • bashlib API
  • ocrd__raise
  • ocrd__log
  • ocrd__minversion
  • ocrd__dumpjson
  • ocrd__usage
  • ocrd__parse_argv
• Testing
• See Also

Introduction

This repository contains the python packages that form the base for tools within the OCR-D ecosphere.

All packages are also published to PyPI.

Installation

NOTE Unless you want to contribute to OCR-D/core, we recommend installation as part of ocrd_all which installs a complete stack of OCR-D-related software.

The easiest way to install is via pip:

pip install ocrd

# or just the functionality you need, e.g.

pip install ocrd_modelfactory

All python software released by OCR-D requires Python 3.6 or higher.

NOTE Some OCR-D-Tools (or even test cases) might reveal an unintended behavior if you have specific environment modifications, like:

• using a custom build of ImageMagick, whose format delegates are different from what OCR-D supposes
• custom Python logging configurations in your personal account

Command line tools

NOTE: All OCR-D CLI tools support a --help flag which shows usage and supported flags, options and arguments.

ocrd CLI

• CLI usage
• Introduction to ocrd workspace
• OCR-D user guide

ocrd-dummy CLI

A minimal OCR-D processor that copies from -I/-input-file-grp to -O/-output-file-grp

Configuration

Almost all behaviour of the OCR-D/core software is configured via CLI options and flags, which can be listed with the --help flag that all CLI support.

Some parts of the software are configured via environement variables:

• OCRD_METS_CACHING: If set to true, access to the METS file is cached, speeding in-memory search and modification.
• OCRD_PROFILE: This variable configures the built-in CPU and memory profiling. If empty, no profiling is done. Otherwise expected to contain any of the following tokens:
  • CPU: Enable CPU profiling of processor runs
  • RSS: Enable RSS memory profiling
  • PSS: Enable proportionate memory profiling
• OCRD_PROFILE_FILE: If set, then the CPU profile is written to this file for later peruse with a analysis tools like snakeviz

Packages

ocrd_utils

Contains utilities and constants, e.g. for logging, path normalization, coordinate calculation etc.

See README for ocrd_utils for further information.

ocrd_models

Contains file format wrappers for PAGE-XML, METS, EXIF metadata etc.

See README for ocrd_models for further information.

ocrd_modelfactory

Code to instantiate models from existing data.

See README for ocrd_modelfactory for further information.

ocrd_validators

Schemas and routines for validating BagIt, ocrd-tool.json, workspaces, METS, page, CLI parameters etc.

See README for ocrd_validators for further information.

ocrd

Depends on all of the above, also contains decorators and classes for creating OCR-D processors and CLIs.

Also contains the command line tool ocrd.

See README for ocrd for further information.

bash library

Builds a bash script that can be sourced by other bash scripts to create OCRD-compliant CLI.

For example:

source `ocrd bashlib filename`
declare -A NAMESPACES MIMETYPES
eval NAMESPACES=( `ocrd bashlib constants NAMESPACES` )
echo ${NAMESPACES[page]}
eval MIMETYPES=( `ocrd bashlib constants EXT_TO_MIME` )
echo ${MIMETYPES[.jpg]}

bashlib CLI

See CLI usage

bashlib API

ocrd__raise

Raise an error and exit.

ocrd__log

Delegate logging to ocrd log

ocrd__minversion

Ensure minimum version

ocrd__dumpjson

Output ocrd-tool.json content verbatim.

Requires $OCRD_TOOL_JSON and $OCRD_TOOL_NAME to be set:

export OCRD_TOOL_JSON=/path/to/ocrd-tool.json
export OCRD_TOOL_NAME=ocrd-foo-bar

(Which you automatically get from ocrd__wrap.)

ocrd__show_resource

Output given resource file's content.

ocrd__list_resources

Output all resource files' names.

ocrd__usage

Print help on CLI usage.

ocrd__parse_argv

Parses arguments according to OCR-D CLI. In doing so, depending on the values passed to it, may delegate to …

• ocrd__raise and exit (if something went wrong)
• ocrd__usage and exit
• ocrd__dumpjson and exit
• ocrd__show_resource and exit
• ocrd__list_resources and exit
• ocrd validate tasks and return

Expects an associative array ("hash"/"dict") ocrd__argv to be defined (to e filled by the parser):

declare -A ocrd__argv=()

ocrd__wrap

Parses an ocrd-tool.json for a specific tool (i.e. processor executable).

(Delegates to ocrd__parse_argv, creating the ocrd__argv associative array.)

Usage: ocrd__wrap PATH/TO/OCRD-TOOL.JSON EXECUTABLE ARGS

For example:

ocrd__wrap $SHAREDIR/ocrd-tool.json ocrd-olena-binarize "$@"

ocrd__input_file

Access information on the input files according to the parsed CLI arguments:

• their file url
• their file ID
• their mimetype
• their pageId

Usage: ocrd__input_file NR KEY

For example:

pageId=`ocrd__input_file 3 pageId`

To be used in conjunction with ocrd bashlib input-files in a loop.

(Requires ocrd__wrap to have been run first.)

Testing

Download assets (make assets)

Test with local files: make test

• Test with remote assets:
  • make test OCRD_BASEURL='https://github.com/OCR-D/assets/raw/master/data/'

See Also

• OCR-D Specifications (Repo)
• OCR-D core API documentation (built here via make docs)
• OCR-D Website (Repo)