Ubuntu

OpenCV installation (from source) instructions for debian-like and Ubuntu distributions.

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

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_contrib/modules/  -D BUILD_opencv_xfeatures2d=ON ../opencv/

make -j5
make install

sh -c 'echo "/usr/local/lib" > /etc/ld.so.conf.d/opencv.conf'
ldconfig