Build instructions for Ubuntu Linux

Build OpenALPR

1. Install prerequisites

sudo apt install -y libopencv-dev libtesseract-dev git cmake build-essential libleptonica-dev liblog4cplus-dev libcurl3-dev

1.1. Install beanstalkd to use alprd (to use as daemon for video stream etc.)

sudo apt install beanstalkd

2. Clone the latest code from GitHub

git clone https://github.com/openalpr/openalpr.git

3. Setup the build directory

cd openalpr/src
mkdir build
cd build

4. setup the compile environment

cmake -DCMAKE_INSTALL_PREFIX:PATH=/usr -DCMAKE_INSTALL_SYSCONFDIR:PATH=/etc ..

5. compile the library

make

6. Install the binaries/libraries to your local system (prefix is /usr)

sudo make install

You should now have the executables alpr in the build folder as well as openalpr-utils-benchmark, openalpr-utils-binarizefontsheet, openalpr-utils-sortstate, openalpr-utils-calibrate, openalpr-utils-tagplates, openalpr-utils-classifychars, openalpr-utils-benchmark, and openalpr-utils-prepcharsfortraining in build/misc_utilities

Test

# US Plate
wget http://plates.openalpr.com/ea7the.jpg
alpr -c us ea7the.jpg

# EU Plate
wget http://plates.openalpr.com/h786poj.jpg
alpr -c eu h786poj.jpg

# GB Plate
wget https://images.cdn.circlesix.co/image/1/640/0/uploads/posts/2021/07/b22c2b504ab94949ea0df2a8789d0727.jpg
alpr -c gb b22c2b504ab94949ea0df2a8789d0727.jpg

Or compile all dependencies manually

1. Make sure that dependencies and required tools are installed

sudo apt-get install -y libpng12-dev libjpeg62-dev libtiff4-dev zlib1g-dev build-essential autoconf automake libtool git-core cmake

2. Install opencv
3. download and install leptonica and tesseract-ocr (tesseract-ocr requires leptonica and at least one language package)

cd /usr/local/src/openalpr/
wget https://github.com/DanBloomberg/leptonica/archive/v1.70.tar.gz
wget https://github.com/tesseract-ocr/tesseract/archive/refs/tags/3.02.02.tar.gz -O tesseract-ocr-3.02.02.tar.gz
wget https://sourceforge.net/projects/tesseract-ocr-alt/files/tesseract-ocr-3.02.eng.tar.gz

4. unpack the tarballs:

tar xf tesseract-ocr-3.02.02.tar.gz 
tar xf tesseract-ocr-3.02.eng.tar.gz
tar xf leptonica-1.70.tar.gz

5. compile leptonica:

cd  /usr/local/src/openalpr/leptonica-1.70/
./configure --prefix=/usr/local
make
make install

6. compile tesseract:

cd /usr/local/src/openalpr/tesseract-ocr/
./autogen.sh
./configure
make
sudo make install
sudo ldconfig

7. clone the openalpr repo to '/usr/local/src/openalpr/' directory

cd /usr/local/src/openalpr/
git clone https://github.com/openalpr/openalpr.git

8. update CMakeLists.txt compile openalpr

cd /usr/local/src/openalpr/openalpr/
gedit CMakeLists.txt &
    SET(OpenCV_DIR "/usr/local/lib")
    SET(Tesseract_DIR "/usr/local/src/openalpr/tesseract-ocr")
cmake ./
make

Note: For Tesseract 3.03 the source files can be downloaded from the main svn branch or https://drive.google.com/folderview?id=0B7l10Bj_LprhQnpSRkpGMGV2eE0&usp=sharing#list.

A README to real-time license plate detection with OpenALPR, OpenCV and Python

There are many things which could go possibly wrong if we slightly move in a different direction while installing this package. Follow these instructions for Ubuntu machines to scale this package for real-time detection with OpenCV and Python. (Mac HomeBrew is broken too but above the scope of this answer)

1. Start from a clean state, remove every apt-package you've installed for openaplr if you've already messed it up. Remove the python binding, if you've set up that too.

apt list --installed | grep alpr
sudo apt-get purge libopenalpr
sudo rm -rf /usr/local/lib/python3.5/dist-packages/openalpr*

2. Follow the official instructions for installing the package on an Ubuntu machine here. Now, this is the catch. Don't follow The Easiest Way described. Follow the The Easy Way (Ubuntu 14.04+). Because, the version which The Easiest Way provides is an older one, which doesn't support recognize_ndarray functionality for python bindings.

3. Once you've completed the steps, go to the git repo you've cloned to your machine during the above installation and install the python bindings. runtime_data folder is also available in this repo, which will be helpful for next step.

cd openalpr/src/bindings/python/
sudo python3 setup.py install

4. While declaring the Alpr object in the script, what they actually meant by

alpr = Alpr("us", "/path/to/openalpr.conf", "/path/to/runtime_data")

is

alpr = Alpr("us", "/etc/openalpr/openalpr.conf", "openalpr/runtime_data/")

5. Now you're all set to grab a video or webcam using cv2.VideoCapture(), feed each frame to alpr.recognize_ndarray() and life is good 💯