1.如果没有装OpenCV，先执行以下指令安装OpenCV

git clone https://github.com/opencv/opencv.git
cd opencv
git remotes/origin/3.4

2.安装完OpenCV之后，执行以下指令下载opencv_contrib

git clone https://github.com/opencv/opencv_contrib/
cd opencv_contrib
git checkout remotes/origin/3.4
cd .. # get out of opencv_contrib folder

3.重新编译OpenCV，参数指定OPENCV_EXTRA_MODULES_PATH目录为opencv_contrib目录

cd opencv
mkdir build
cd build
cmake -D CMAKE_BUILD_TYPE=RELEASE -D OPENCV_ENABLE_NONFREE=ON -D OPENCV_EXTRA_MODULES_PATH=../opencv_contrib/modules -D WITH_GTK=ON ..
# 如果OpenCV编译报各种错，尝试执行以下指令
# cmake -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local -D WITH_TBB=ON -D BUILD_NEW_PYTHON_SUPPORT=ON -D WITH_V4L=ON -D WITH_QT=ON -D WITH_OPENGL=ON -D WITH_GTK=ON -DBUILD_TIFF=ON  -D OPENCV_EXTRA_MODULES_PATH=../opencv_contrib/modules -D  OPENCV_ENABLE_NONFREE=ON ..
sudo make
sudo make install