How to install OpenCV on Ubuntu 18.04

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OpenCV (Open Source Computer Vision Library) is an open source computer vision library and has bindings for C ++, Python, and Java. It is used for a variety of applications including medical image analysis, street view image stitching, surveillance video, face detection and recognition, moving object tracking, 3D model extraction, and much more. OpenCV
can take advantage of multi-core processing and provide GPU acceleration for real-time operation.

This tutorial explains how to install OpenCV on Ubuntu 18.04.

For most people, the easiest way to install OpenCV on Ubuntu is to install it using the apt package management tool. If you want to install the latest stable version of OpenCV from source, scroll down to the Install OpenCV from the source
Section of this tutorial.

Choose one of the installation options that works best for you.

Install OpenCV from the Ubuntu repository

The OpenCV package is available in the Ubuntu 18.04 distribution repository. At the time of writing, the version in the repositories is 3.2 which is not the latest version.

To install OpenCV from the Ubuntu 18.04 repositories, do the following:

  1. Update the package index and install the OpenCV package by typing:

    sudo apt updatesudo apt install python3-opencv

    The above command installs all of the packages required to run OpenCV.

  2. To check the installation, import the cv2 Module and print the OpenCV version:

    python3 -c "import cv2; print(cv2.__version__)"
    3.2.0

The standard Python version in Ubuntu 18.04 LTS is version 3.6. If you want to install OpenCV with Python 2 bindings, install the python-opencv Package.

Install OpenCV from the source

Building the OpenCV library from source code is the recommended method for installing OpenCV. It will be optimized for your particular system and you will have complete control over the build options.

To install the latest OpenCV version from the source, do the following:

  1. Install the required dependencies:

    sudo 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
  2. Clone the OpenCV and OpenCV contrib repositories:

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

    At the time of writing, the default version on the Github repositories is version 4.2.0. If you want to install an older version of OpenCV, cd on both opencv and opencv_contrib Directories and run git checkout <opencv-version>

  3. After the download is complete, create a temporary build directory and switch to it:

    cd ~/opencv_build/opencvmkdir 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 complete you will see the following:

  4. Start the compilation process:

    make -j8

    Modify the -j Flag according to your processor. If you don’t know the number of cores your processor has, you can get it by typing. detect nproc.

    Compilation can take several minutes or longer, depending on the system configuration. Once it finishes you will see something like below:

  5. Install OpenCV with:

    sudo make install
  6. To check if OpenCV was installed successfully, enter the following command and you should see the OpenCV version:

    pkg-config --modversion opencv4
    4.2.0
    python3 -c "import cv2; print(cv2.__version__)"
    4.2.0-dev

Conclusion

We showed you two different ways to install OpenCV on your Ubuntu 18.04 server. Which method you choose depends on your needs and preferences. While installing the packaged version from the Ubuntu repository is easier, building OpenCV from source gives you more flexibility and should be your first option when installing OpenCV.

If you have any questions or feedback, please feel free to comment below.