How to Installing OpenCV from the Source

What is OpenCV

OpenCV (Open Source Computer Vision Library) is an open source computer vision and machine learning software library. OpenCV was built to provide a common infrastructure for computer vision applications and to accelerate the use of machine perception in the commercial products. 

Install the required dependencies

apt install build-essential cmake git pkg-config libgtk-3-dev libavcodec-dev libavformat-dev libswscale-dev libv4l-dev libxvidcore-dev libx264-dev libjpeg-dev libpng-dev libtiff-dev gfortran openexr libatlas-base-dev python3-dev python3-numpy libtbb2 libtbb-dev libdc1394-22-dev 

Clone the OpenCV’s and OpenCV contrib repositories

mkdir ~/opencv_build && cd ~/opencv_build
git clone https://github.com/opencv/opencv.git
git clone https://github.com/opencv/opencv_contrib.git 

Once the download is complete, create a temporary build directory, and switch to it

cd ~/opencv_build/opencv

mkdir build && cd build

Set up the OpenCV build with CMake

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 ..

When the CMake build system is finalized, you will see something like below

Start the compilation process

make -j8

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.

The compilation may take several minutes or more, depending on your system configuration. Once it is completed you will see something like below:

Install OpenCV

make install

To verify whether OpenCV has been installed successfully, type the following command and you should see the OpenCV version

pkg-config --modversion opencv4