https://www.cnblogs.com/pyrokine/p/8921285.html
modify python (for build) /usr/bin/python3.5
numpy
gtk
cmake -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local -D INSTALL_C_EXAMPLES=OFF -D INSTALL_PYTHON_EXAMPLES=OFF -D OPENCV_EXTRA_MODULES_PATH=/home/pi/Downloads/opencv_contrib-3.4.1/modules -D BUILD_EXAMPLES=OFF -D WITH_LIBV4L=ON -D HAVE_GTK=ON -D BUILD_opencv_python2=OFF -D BUILD_opencv_python3=ON PYTHON3_EXECUTABLE=/usr/bin/python3.5 PYTHON_INCLUDE_DIR=/usr/include/python3.5 PYTHON_LIBRARY=/usr/lib/arm-linux-gnueabihf/libpython3.5m.so PYTHON3_NUMPY_INCLUDE_DIRS=/home/pi/.local/lib/python3.5/site-packages/numpy/core/include ..