Install OpenCV on AlmaLinux 8

In this guide, you will learn to Install OpenCV by using the DNF package manager and From Source on AlmaLinux 8. OpenCV is an open-source library that can perform tasks such as face detection, objection tracking, landmark detection, and much more. Also, it supports multiple languages including Python, java, and C++. 

Steps To Install and Configure OpenCV on AlmaLinux 8

To set up OpenCV, you must have access to your server as a non-root user with sudo privileges. To do this, you can visit this guide on Initial Server Setup with AlmaLinux 8.

Now proceed to the following steps to complete this guide.

Step 1 – OpenCV Installation with DFN on AlmaLinux 8

At this point, you can easily install your OpenCV from the AlmaLinux 8 repository.

First, update your local package index with the command below:

sudo dnf update -y

Next, install the Epel repository on your server :

sudo dnf install epel-release -y

Enable PowerTools by using the command below:

sudo dnf config-manager --set-enabled powertools

Then, use the command below to install OpenCV:

sudo dnf install opencv opencv-devel -y

This command will install all packages necessary to run OpenCV.

You can verify your installation with the following command:

pkg-config --modversion opencv 
Output
3.4.6

Step 2 – OpenCV Installation From Source on AlmaLinux 8

It’s recommended to use this way to install OpenCV on your server.  It will be optimized for your particular system, and you will have complete control over the build options.

To install the latest and stable version of OpenCV from the source follow the steps below.

First, update your local package index with the following command:

sudo dnf update -y

Required Dependencies for OpenCV on AlmaLinux 8

Then, you need to install the dependencies with the following command:

sudo dnf -y install epel-release git gcc gcc-c++ cmake3 qt5-qtbase-devel python3 python3-devel python3-pip cmake python3-devel python3-numpy gtk2-devel libpng-devel jasper-devel openexr-devel libwebp-devel libjpeg-turbo-devel libtiff-devel tbb-devel libv4l-devel eigen3-devel freeglut-devel mesa-libGL mesa-libGL-devel boost boost-thread boost-devel gstreamer1-plugins-base

Now create a directory for OpenCV on AlmaLinux 8 and switch to it with the following command:

# sudo mkdir ~/opencv_build 
# sudo cd ~/opencv_build

Clone OpenCV Repositories

Next, you need to clone the OpenCV and OpenCV contrib repositories with the following commands:

# sudo git clone https://github.com/opencv/opencv.git
# sudo git clone https://github.com/opencv/opencv_contrib.git

When your download is completed, create a temporary build directory and switch to it with the following command:

# sudo cd ~/opencv_build/opencv
# sudo mkdir build
# sudo cd build

Compile and Build OpenCV

Here you need to set up OpenCV build with CMake on AlmaLinux 8:

sudo cmake ../

In your output you will see:

Output
-- Configuring done
-- Generating done
-- Build files have been written to: /root/opencv_build/opencv/build

Now start the compilation process:

make -j2

Note: Modify the -j flag according to your processor. If you do not know the number of cores in your processor, you can find it by typing nproc.

This will take some minutes or more to complete.

In your output you will see:

Output
...
[100%] Building CXX object modules/gapi/CMakeFiles/opencv_test_gapi.dir/test/util/variant_tests.cpp.o
[100%] Linking CXX executable ../../bin/opencv_test_gapi
[100%] Built target opencv_test_gapi

Now you can install OpenCV with the following command:

sudo make install

Finally, create a symlink file opencv4.pc to the directory /usr/share/pkgconfig and run ldconfig to rebuild the library’s cache:

# sudo ln -s /usr/local/lib64/pkgconfig/opencv4.pc /usr/share/pkgconfig/ 
# sudo ldconfig

To enable Python modules cv2 run the following command below:

python3 -c "import cv2; print(cv2.__version__)"
Output
4.8.0-dev

That’s it you have successfully installed OpenCV on AlmaLinux 8.

For more information, you can visit OpenCV Official site.

Conclusion

At this point, you have learned to Install OpenCV with the DNF package manager and also build it from source on AlmaLinux 8. It is recommended to build and install OpenCV from the source in the latest version.

Hope you enjoy it. You may like these articles on the Orcacore website:

Web Browsing on AlmaLinux Terminal

Configure Rsyslog in AlmaLinux

10 Useful ncat Commands on AlmaLinux

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