Nextcloud: Install OCR

The OCR app for Nextcloud 12 comes with a Docker container which has any prerequisites installed. The communication between the Docker container and the host goes over Redis.

Install the OCR app of the Nextcloud app store

The minimum required Nextcloud version is 12, as well as Docker and Redis are mandatory.

After installing the app of the Nextcloud app store, goto the redis folder within the app folder

cd /var/www/nextcloud/apps/ocr/redis


Edit redis.conf

port 6380

Install the Docker container with the Redis instance

docker build --build-arg PASSWORD="secretpassword" -t username/redis .

Replace username with your real username.

Sending build context to Docker daemon 45.06kB
Step 1/6 : FROM redis
latest: Pulling from library/redis
b0568b191983: Pull complete
6637dc5b29fe: Pull complete
7b4314315f15: Pull complete
2fd86759b5ff: Pull complete
0f04862b5a3b: Pull complete
2db0056aa977: Pull complete
Digest: sha256:2feb46bc240662176a27fd62dd1718522dd386ab7bf84276bb1e3140f9d4baaa
Status: Downloaded newer image for redis:latest
 ---> c5355f8853e4
Step 2/6 : LABEL maintainer "[email protected]" description "This image serves the redis instance for the ocr worker and the nextcloud ocr app." vendor "Janis Koehr"
 ---> Running in 5c89b99bfcce
 ---> 8038c0d70f13
Removing intermediate container 5c89b99bfcce
 ---> Running in cbc6b660c018
 ---> d807564bb364
Removing intermediate container cbc6b660c018
Step 4/6 : COPY redis.conf /usr/local/etc/redis/redis.conf
 ---> 172b616ed583
Removing intermediate container 620b7227747e
Step 5/6 : RUN if [ -n "$PASSWORD" ]; then echo "requirepass $PASSWORD" >> /usr/local/etc/redis/redis.conf; fi
 ---> Running in 445d973832e1
 ---> bf9cf41a4ffa
Removing intermediate container 445d973832e1
Step 6/6 : CMD redis-server /usr/local/etc/redis/redis.conf
 ---> Running in 86d3fda8d40e
 ---> 0f86b1ed94fb
Removing intermediate container 86d3fda8d40e
Successfully built 0f86b1ed94fb
Successfully tagged username/redis:latest

Then go to the worker directory within the app folder

cd ../worker


Install the Tesseract Docker Container

docker build --build-arg LANGUAGES="tesseract-ocr-deu tesseract-ocr-deu-frak tesseract-ocr-osd tesseract-ocr-equ" -t username/ocr .

Replace username with your real username. Add as many languages as needed to the command line.

Setup a Custom Docker Network

docker network create --driver bridge isolated_ocr


docker run --name redis --network=isolated_ocr -p 6380:6380 -d username/redis

Replace username with your real username.


Setup a tempdirectory where the webserver can write temporarely

vi /var/www/nextcloud/config/config.php
'tempdirectory' => '/tmp/nextcloudtemp',

Don’t forget to add the path to open_basedir.

Run the Docker container

docker run --name ocr --network=isolated_ocr -e "NODE_ENV=production" -e "REDIS_HOST=redis" -e "REDIS_PORT=6380" -e "REDIS_DB=0" -e "REDIS_PASSWORD=secretpassword" -v /path/to/data/directory/of/nextcloud:/home/node/data:ro -v /path/to/tmp:/home/node/output -d username/ocr

Adjust the secretpassword (which you have created before), /path/to/data/directory/of/nextcloud, /path/to/tmp, username.

Configure the OCR App

Start OCR

Go to the files section, select OCR of a file

Choose OCR language

and select Process.

See also