How to Install Open Source Computer Vision Library (OpenCV) on CentOS 8

OpenCV stands for “Open Source Computer Vision Library” is an open-source cross-platform computer vision algorithm library that can be used in all kinds of visual processing areas, such as facial recognition, gesture recognition and motion tracking. It is specially designed to take advantage of multi-core processing and features GPU acceleration for real-time operation. It can be installed on several operating systems, including Windows, Linux, Android, iOS, etc.

In this tutorial, we will explain how to install OpenCV on CentOS 8.

Prerequisites

• A server running CentOS 8.
• A root password is set up on your server.

Install Required Packages

By default, OpenCV is not available in the CentOS 8 default repository. So you will need to compile it from the source. In order to compile the OpenCV, you will need to install required dependencies in your system. You can install all of them with the following command:

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

Once all the packages are installed, you can proceed to the next step.

Install OpenCV

First, create a build directory for OpenCV with the following command:

mkdir -p ~/opencv_build

Next, change the directory to opencv_build and download the latest version of OpenCV and OpenCV contrib source with the following command:

cd ~/opencv_build

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

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

Next, change the directory to opencv and create a temporary build directory with the following command:

cd opencv

mkdir build

Next, change the directory to the build directory and configure the OpenCV with the following command:

cmake -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local -D INSTALL_C_EXAMPLES=ON -D INSTALL_PYTHON_EXAMPLES=ON -D OPENCV_GENERATE_PKGCONFIG=ON -D OPENCV_EXTRA_MODULES_PATH=~/opencv_build/opencv_contrib/modules -D BUILD_EXAMPLES=ON ..

You should get the following screen:

<img alt="Build OpenCV" data-ezsrc="https://kirelos.com/wp-content/uploads/2020/05/echo/p1.png5ecffa506a0c9.jpg" ezimgfmt="rs rscb1 src ng ngcb1" height="469" src="data:image/svg xml,” width=”750″>

Next, start the compilation with the following command:

make -j4

You should get the following screen:

<img alt="Make command" data-ezsrc="https://kirelos.com/wp-content/uploads/2020/05/echo/p21.png5ecffa50951df.jpg" ezimgfmt="rs rscb1 src ng ngcb1" height="389" src="data:image/svg xml,” width=”750″>

Finally, install the OpenCV with the following command:

make install

You should get the following screen:

<img alt="Make install" data-ezsrc="https://kirelos.com/wp-content/uploads/2020/05/echo/p3.png5ecffa50c3761.jpg" ezimgfmt="rs rscb1 src ng ngcb1" height="531" src="data:image/svg xml,” width=”750″>

Next, create a symbolic link of opencv4.pc to the /usr/share/pkgconfig directory:

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

Next, rebuild the libraries cache with the following command:

ldconfig

Next, you can verify the OpenCV version with the following command:

pkg-config --modversion opencv4

You should get the following output:

4.3.0

You can also verify the Python cv2 module with the following command:

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

You should get the following output:

4.3.0-dev

Conclusion

Congratulations! you have successfully installed OpenCV from the source. For more information about OpenCV, you can go to the official web site of OpenCV directly.