This is a persistent docker service provided with volume mapping as a way to extend applications that need the ability to convert documents into pngs. A common scenario for this would be generating thumbnail files of documents for a data store.
The name of this project is a little misleading, as libreoffice is used only for the initial conversion of the documents into a pdf, which is then converted to png using imagemagick. This is done because I found that the quality of documents directly into png using only libreoffice was of poor quality. This was especially notiable when converting from PDFs as headless mode was having difficulty processing embedded fonts, whereas imagemagick handles it flawlessly.
Simply use docker's volume mapping to mount two volumes to a container. You'll need an in, mapped to /mnt/in and an out, mapped to /mnt/out.
To do this with docker run, you can do docker run -d -P -v ./media:/mnt/in -v ./thumbs:/mnt/out
It's highly recommended that you DO NOT MAP THE SAME DIRECTORY TO IN AND OUT
An example file is provided that demonstrates how to use the container with docker-compose and django, showing the thumbnails of documents that have been uploaded into a database.
Since the watcher.sh is just a simple inotify script, it's possible with a very little modification to just use it as a systemd script if you wish to provide a service using already installed applications without the overhead of docker. In fact, docker never really should be necessary, this is just a docker project for ease of deployment which may help one quickly extend an existing system.