#Installing opencv with non free libs:
Needs to be built from source in order to use the non-free algorithms:
Clone the required repositories(in your home directory, do "cd ~" to go to home directory):
Initialize a build directory:
mkdir opencvbuild
Clone OpenCV
git clone https://github.com/opencv/opencv
Clone OpenCV-Contrib
git clone https://github.com/opencv/opencv_contrib
Go to the opencv folder
cd opencv
Now set the cmake flags as required, in our case we enable non-free and install the extra modules from opencv-contrib
cmake -D CMAKE_BUILD_TYPE=RELEASE \
-D CMAKE_INSTALL_PREFIX=/usr/local \
-D OPENCV_EXTRA_MODULES_PATH=~/opencv_contrib/modules \
-D BUILD_opencv_python2=OFF \
-D BUILD_opencv_python3=ON \
-D OPENCV_ENABLE_NONFREE=ON \
-D BUILD_EXAMPLES=ON
-S ./ \
-B ~/opencvbuild \
..
Now set the number of CPU cores the package would build on and start the building process, higher is better but spare at least 1 or 2 cores from total number of cores
make -j6 # the number 6 is the number of CPU cores.
Now to copy the built files to their respective locations do:
sudo make install
Windows (assuming a 64 bit CPU arch):
Download and install cmake, add cmake to PATH variable during installation
```https://github.com/Kitware/CMake/releases/download/v3.18.2/cmake-3.18.2-win64-x64.msi```
Install git-bash. Don't add git to PATH variable during installation
```https://github.com/git-for-windows/git/releases/download/v2.28.0.windows.1/Git-2.28.0-64-bit.exe```
Run git-bash. You observe a command line window. Suppose you want to build opencv and opencv_contrib in c:/lib
In git command line enter following command (if folder does not exist) :
```
mkdir /c/lib
cd /c/lib
```
Download and copy installOCV.sh script to c:/lib
Run in git command line:
```./installOCV.sh```
Set the OpenCV environment variable and add it to the systems path
```setx -m OPENCV_DIR D:\OpenCV\Build\x64\vc14```