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OCRmyPDF adds an OCR text layer to scanned PDF files, allowing them to be searched

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OCRmyPDF

OCRmyPDF adds an OCR text layer to scanned PDF files, allowing them to be searched.

Main features

  • Generates a searchable PDF/A file from a regular PDF
  • Places OCR text accurately below the image to ease copy / paste
  • Keeps the exact resolution of the original embedded images
  • When possible, inserts OCR information as a "lossless" operation without rendering vector information
  • Keeps file size about the same
  • If requested deskews and/or cleans the image before performing OCR
  • Validates input and output files
  • Provides debug mode to enable easy verification of the OCR results
  • Processes pages in parallel when more than one CPU core is available
  • Uses Tesseract OCR engine
  • Supports more than 100 languages recognized by Tesseract
  • Battle-tested on thousands of PDFs, a test suite and continuous integration

For details: please consult the release notes.

Motivation

I searched the web for a free command line tool to OCR PDF files on Linux/UNIX: I found many, but none of them were really satisfying.

  • Either they produced PDF files with misplaced text under the image (making copy/paste impossible)
  • Or they did not handle accents and multilingual characters
  • Or they changed the resolution of the embedded images
  • Or they generated ridiculously large PDF files
  • Or they crashed when trying to OCR some of my PDF files
  • Or they did not produce valid PDF files (even though they were readable with my current PDF reader)
  • On top of that none of them produced PDF/A files (format dedicated for long time storage)

... so I decided to develop my own tool (using various existing scripts as an inspiration)

Installation

Download OCRmyPDF here: https://github.com/jbarlow83/OCRmyPDF/releases

These steps describe how to install OCRmyPDF on your system.

If you prefer to install from source or install OCRmyPDF to a Python virtual environment, see steps for Installing HEAD revision from sources.

Installing on Debian and Ubuntu

Users of Debian 9 or later or Ubuntu 16.10 or later may simply apt-get install ocrmypdf.

Installing the Docker image

For many users, installing the Docker image will be easier than installing all of OCRmyPDF's dependencies. For Windows, it is the only option.

If you have Docker installed on your system, you can install a Docker image of the latest release.

Follow the Docker installation instructions for your platform. If you can run this command successfully, your system is ready to download and execute the image:

docker run hello-world

OCRmyPDF will use all available CPU cores. By default, the VirtualBox machine instance on Windows and OS X has only a single CPU core enabled. Use the VirtualBox Manager to determine the name of your Docker engine host, and then follow these optional steps to enable multiple CPUs:

# Optional step for Mac OS X users
docker-machine stop "yourVM"
VBoxManage modifyvm "yourVM" --cpus 2  # or whatever number of core is desired
docker-machine start "yourVM"
eval $(docker-machine env "yourVM")

Assuming you have a Docker engine running somewhere, you can run these commands to download the image:

docker pull jbarlow83/ocrmypdf

Then tag it to give a more convenient name, just ocrmypdf:

docker tag jbarlow83/ocrmypdf ocrmypdf

This image contains language packs for English, French, Spanish and German. The alternative "polyglot" image provides all available language packs:

# Alternative step: If you need all language packs
docker pull jbarlow83/ocrmypdf-polyglot
docker tag jbarlow83/ocrmypdf-polyglot ocrmypdf

You can then run ocrmypdf using the command:

docker run ocrmypdf --help

To execute the OCRmyPDF on a local file, you must provide a writable volume to the Docker image, such as this in this template:

docker run -v "$(pwd):/home/docker" <other docker arguments>   ocrmypdf <your arguments to ocrmypdf>

In this worked example, the current working directory contains an input file called test.pdf and the output will go to output.pdf:

docker run -v "$(pwd):/home/docker"   ocrmypdf --skip-text test.pdf output.pdf

Note that ocrmypdf has its own separate -v VERBOSITYLEVEL argument to control debug verbosity. All Docker arguments should before the ocrmypdf image name and all arguments to ocrmypdf should be listed after.

Installing on Mac OS X

These instructions probably work on all Mac OS X versions later than 10.7 (Lion). OCRmyPDF is known to work on Yosemite and El Capitan, and regularly tested on El Capitan.

If it's not already present, install Homebrew.

Update Homebrew:

brew update

Install or upgrade the required Homebrew packages, if any are missing:

brew install libpng openjpeg jbig2dec libtiff     # image libraries
brew install qpdf
brew install ghostscript
brew install python3
brew install libxml2 libffi leptonica
brew install unpaper   # optional

Install the required Tesseract OCR engine with the language packs you plan to use:

brew install tesseract                       # Option 1: for English, French, German, Spanish
brew install tesseract --with-all-languages  # Option 2: for all language packs

Update the homebrew pip and install Pillow:

pip3 install --upgrade pip
pip3 install --upgrade pillow

You can then install OCRmyPDF from PyPI:

pip3 install ocrmypdf

The command line program should now be available:

ocrmypdf --help

Installing on Ubuntu 14.04 LTS

Installing on Ubuntu 14.04 LTS (trusty) is more difficult than some other options, because of bugs in Python package installation.

Add new "apt" repositories needed for backports of Ghostscript 9.16 and libav-11, which supports unpaper 6.1. This will replace Ghostscript on your system.

sudo add-apt-repository ppa:vshn/ghostscript -y
sudo add-apt-repository ppa:heyarje/libav-11 -y

Update apt-get:

sudo apt-get update
sudo apt-get upgrade

Install system dependencies:

sudo apt-get install \
   zlib1g-dev \
   libjpeg-dev \
   libffi-dev \
   libavformat56 libavcodec56 libavutil54 \
   ghostscript \
   tesseract-ocr \
   qpdf \
   python3-pip \
   python3-pil \
   python3-pytest \
   python3-reportlab

If you wish install OCRmyPDF to the system Python, then install as follows (note this installs new packages into your system Python, which could interfere with other programs):

sudo pip3 install ocrmypdf

If you wish to install OCRmyPDF to a virtual environment to isolate the system Python, you can follow these steps. This includes a workaround for a known, unresolved issue in Ubuntu 14.04's ensurepip package:

sudo apt-get install python3-venv
python3 -m venv venv-ocrmypdf --without-pip
source venv-ocrmypdf/bin/activate
wget -O - -o /dev/null https://bootstrap.pypa.io/get-pip.py | python
deactivate
python3 -m venv --system-site-packages venv-ocrmypdf
source venv-ocrmypdf/bin/activate
pip install ocrmypdf

These installation instructions omit the optional dependency unpaper, which is only available at version 0.4.2 in Ubuntu 14.04. The author could not find a backport of unpaper and is not motivated to figure how to set up a Ubuntu PPA to distribute it. You can create a .deb package to do the job of installing unpaper 6.1 (for x86 64-bit only):

wget -q https://dl.dropboxusercontent.com/u/28971240/unpaper_6.1-1.deb -O unpaper_6.1-1.deb
sudo dpkg -i unpaper_6.1-1.deb

Installing on Windows

Direct installation on Windows is not possible. Install the Docker container as described above. Ensure that your command prompt can run the docker "hello world" container.

Running on Windows

The command line syntax to run ocrmypdf from a command prompt will resemble:

docker run -v /c/Users/sampleuser:/home/docker ocrmypdf --skip-text test.pdf output.pdf

where /c/Users/sampleuser is a Unix representation of the Windows path C:\Users\sampleuser, assuming a user named "sampleuser" is running ocrmypdf on a file in their home directory, and the files "test.pdf" and "output.pdf" are in the sampleuser folder. The Windows user must have read and write permissions.

Installing HEAD revision from sources

If you have git and python3.4 or python3.5 installed, you can install from source. When the pip installer runs, it will alert you if dependencies are missing.

To install the HEAD revision from sources in the current Python 3 environment:

pip3 install git+https://github.com/jbarlow83/OCRmyPDF.git

Or, to install in development mode, allowing customization of OCRmyPDF, use the -e flag:

pip3 install -e git+https://github.com/jbarlow83/OCRmyPDF.git

On certain Linux distributions such as Ubuntu, you may need to use run the install command as superuser:

sudo pip3 install [-e] git+https://github.com/jbarlow83/OCRmyPDF.git

Note that this will alter your system's Python distribution. If you prefer to not install as superuser, you can install the package in a Python virtual environment:

git clone -b master https://github.com/jbarlow83/OCRmyPDF.git
python3 -m venv
source venv/bin/activate
cd OCRmyPDF
pip3 install .

However, ocrmypdf will only be accessible on the system PATH after you activate the virtual environment.

To run the program:

ocrmypdf --help

If not yet installed, the script will notify you about dependencies that need to be installed. The script requires specific versions of the dependencies. Older version than the ones mentioned in the release notes are likely not to be compatible to OCRmyPDF.

Languages

OCRmyPDF uses Tesseract for OCR, and relies on its language packs. For Linux users, you can often find packages that provide language packs:

# Display a list of all Tesseract language packs
apt-cache search tesseract-ocr

# Debian/Ubuntu users
sudo apt-get install tesseract-ocr-chi-sim  # Example: Install Chinese Simplified language back

You can then pass the -l LANG argument to OCRmyPDF to give a hint as to what languages it should search for. Multiple languages can be requested.

Support

Once ocrmypdf is installed, the built-in help which explains the command syntax and options can be accessed via:

ocrmypdf --help

The Wiki page also contains some tips and suggests.

If you detect an issue, please:

  • Check whether your issue is already known
  • If no problem report exists on github, please create one here: https://github.com/jbarlow83/OCRmyPDF/issues
  • Describe your problem thoroughly
  • Append the console output of the script when running the debug mode (-v 1 option)
  • If possible provide your input PDF file as well as the content of the temporary folder (using a file sharing service like Dropbox)

Press & Media

Disclaimer

The software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

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OCRmyPDF adds an OCR text layer to scanned PDF files, allowing them to be searched

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