OCRmyPDF Docker image¶
OCRmyPDF is also available in Docker images that packages recent versions of all dependencies.
For users who already have Docker installed this may be an easy and convenient option.
On platforms other than Linux, Docker runs in a virtual machine, and so may be less performant. You may also want to adjust the Docker virtual machine’s memory and CPU allocation. On Linux, the Docker image runs natively and performance is comparable to a system installation.
Installing the Docker image¶
If you have Docker installed on your system, you can install a Docker image of the latest release.
If you can run this command successfully, your system is ready to download and execute the image:
docker run hello-world
To install:
docker pull jbarlow83/ocrmypdf-alpine
The ocrmypdf image is also available, but is deprecated and will be removed
in the future.
OCRmyPDF will use all available CPU cores. See the Docker documentation for adjusting memory and CPU on other platforms.
Using the Docker image on the command line¶
Unlike typical Docker containers, in this section the OCRmyPDF Docker
container is ephemeral – it runs for one OCR job and terminates, just like a
command line program. We are using Docker to deliver an application (as opposed
to the more conventional case, where a Docker container runs as a server).
For that reason we usually use the --rm argument to delete the container
when it exits.
To start a Docker container (instance of the image):
docker tag jbarlow83/ocrmypdf ocrmypdf
docker run --rm -i ocrmypdf (... all other arguments here...) - -
For convenience, create a shell alias to hide the Docker command. It is easier to send the input file as stdin and read the output from stdout – this avoids the messy permission issues with Docker entirely.
alias docker_ocrmypdf='docker run --rm -i ocrmypdf'
docker_ocrmypdf --version # runs docker version
docker_ocrmypdf - - <input.pdf >output.pdf
Or in the wonderful fish shell:
alias docker_ocrmypdf 'docker run --rm ocrmypdf'
funcsave docker_ocrmypdf
Alternately, you could mount the local current working directory as a Docker volume:
alias docker_ocrmypdf='docker run --rm -i --user "$(id -u):$(id -g)" --workdir /data -v "$PWD:/data" ocrmypdf'
docker_ocrmypdf /data/input.pdf /data/output.pdf
Adding languages to the Docker image¶
By default the Docker image includes English, German, Simplified Chinese, French, Portuguese and Spanish, the most popular languages for OCRmyPDF users based on feedback. You may add other languages by creating a new Dockerfile based on the public one.
FROM jbarlow83/ocrmypdf
# Example: add Italian
RUN apt install tesseract-ocr-ita
To install language packs (training data) such as the tessdata_best suite or custom data, you first need to determine the version of Tesseract data files, which may differ from the Tesseract program version. Use this command to determine the data file version:
docker run -i --rm --entrypoint /bin/ls jbarlow83/ocrmypdf /usr/share/tesseract-ocr
As of 2021, the data file version is probably 4.00.
You can then add new data with either a Dockerfile:
FROM jbarlow83/ocrmypdf:{TAG}
# Example: add a tessdata_best file
COPY chi_tra_vert.traineddata /usr/share/tesseract-ocr/<data version>/tessdata/
When creating your own image, you should always pin a specific version of the OCRmyPDF Docker image. This ensures that your image will not break when a new version of OCRmyPDF is released.
Alternately, you can copy training data into a Docker container as follows:
docker cp mycustomtraining.traineddata name_of_container:/usr/share/tesseract-ocr/<tesseract version>/tessdata/
Extending the Docker image¶
You can extend the Docker image with your own customizations, similar to the way it is extended to add language packs.
Note that the Docker image is subject to change at any time. For example, the base image may be updated to a newer version of Ubuntu or Debian. Such changes will be noted in the release notes but might occur at minor versions releases, unless the way a “casual” user of the Docker image is affected.
If you extend the Docker image, you should pin a specific version of the OCRmyPDF Docker image.
Executing the test suite¶
The OCRmyPDF test suite is installed with image. To run it:
docker run --rm --entrypoint python jbarlow83/ocrmypdf -m pytest
Accessing the shell¶
To use the shell in the Docker image:
docker run -it --entrypoint sh jbarlow83/ocrmypdf
Using the OCRmyPDF web service wrapper¶
The OCRmyPDF Docker image includes an example, barebones HTTP web service. The webservice may be launched as follows:
docker run --entrypoint python -p 5000:5000 jbarlow83/ocrmypdf webservice.py
We omit the --rm parameter so that the container will not be
automatically deleted when it exits.
This will configure the machine to listen on port 5000. On Linux machines
this is port 5000 of localhost. On macOS or Windows machines running
Docker, this is port 5000 of the virtual machine that runs your Docker
images. You can find its IP address using the command docker-machine ip.
Unlike command line usage this program will open a socket and wait for connections.
Warning
The OCRmyPDF web service wrapper is intended for demonstration or development. It provides no security, no authentication, no protection against denial of service attacks, and no load balancing. The default Flask WSGI server is used, which is intended for development only. The server is single-threaded and so can respond to only one client at a time. While running OCR, it cannot respond to any other clients.
Clients must keep their open connection while waiting for OCR to complete. This may entail setting a long timeout; this interface is more useful for internal HTTP API calls.
Unlike the rest of OCRmyPDF, this web service is licensed under the Affero GPLv3 (AGPLv3) since Ghostscript is also licensed in this way.
In addition to the above, please read our general remarks on using OCRmyPDF as a service.