opencv_ubuntu

opencv_ubuntu

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

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

cd ~/opencv_build/opencv
mkdir build && cd build

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 ..
    
 make -j8
 
 sudo make install
 pkg-config --modversion opencv4

Confirmed working on Ubuntu 18.04 for building OpenCV 4. But there are some mistakes on this script, hope you could fix them. sudo are misplaced in line 1,2,3,4. make j8 should be make -j8.

Thanks for your comment @YiqinZhao