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Install OpenCV and Python (UBUNTU)

In this post, we will provide step by step instructions for installing OpenCV 3  (Python) on Ubuntu.

Step 1: Update packages

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sudo apt-get update
sudo apt-get upgrade

Step 2: Install OS libraries

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Remove any previous installations of x264</h3>
sudo apt-get remove x264 libx264-dev
We will Install dependencies now
sudo apt-get install build-essential checkinstall cmake pkg-config yasm
sudo apt-get install git gfortran
sudo apt-get install libjpeg8-dev libjasper-dev libpng12-dev
# If you are using Ubuntu 14.04
sudo apt-get install libtiff4-dev
# If you are using Ubuntu 16.04
sudo apt-get install libtiff5-dev
sudo apt-get install libavcodec-dev libavformat-dev libswscale-dev libdc1394-22-dev
sudo apt-get install libxine2-dev libv4l-dev
sudo apt-get install libgstreamer0.10-dev libgstreamer-plugins-base0.10-dev
sudo apt-get install qt5-default libgtk2.0-dev libtbb-dev
sudo apt-get install libatlas-base-dev
sudo apt-get install libfaac-dev libmp3lame-dev libtheora-dev
sudo apt-get install libvorbis-dev libxvidcore-dev
sudo apt-get install libopencore-amrnb-dev libopencore-amrwb-dev
sudo apt-get install x264 v4l-utils
# Optional dependencies
sudo apt-get install libprotobuf-dev protobuf-compiler
sudo apt-get install libgoogle-glog-dev libgflags-dev
sudo apt-get install libgphoto2-dev libeigen3-dev libhdf5-dev doxygen

Step 3: Install Python libraries

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sudo apt-get install python-dev python-pip python3-dev python3-pip
sudo -H pip2 install -U pip numpy
sudo -H pip3 install -U pip numpy

We will use Virtual Environment to install Python libraries. It is generally a good practice in order to separate your project environment and global environment.

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# Install virtual environment
sudo pip2 install virtualenv virtualenvwrapper
sudo pip3 install virtualenv virtualenvwrapper
echo "# Virtual Environment Wrapper"  >> ~/.bashrc
echo "source /usr/local/bin/virtualenvwrapper.sh" >> ~/.bashrc
source ~/.bashrc
 
############ For Python 2 ############
# create virtual environment
mkvirtualenv facecourse-py2 -p python2
workon facecourse-py2
 
# now install python libraries within this virtual environment
pip install numpy scipy matplotlib scikit-image scikit-learn ipython
 
# quit virtual environment
deactivate
######################################
 
############ For Python 3 ############
# create virtual environment
mkvirtualenv facecourse-py3 -p python3
workon facecourse-py3
 
# now install python libraries within this virtual environment
pip install numpy scipy matplotlib scikit-image scikit-learn ipython
 
# quit virtual environment
deactivate
######################################

Step 4: Download OpenCV and OpenCV_contrib

We will download opencv and opencv_contrib packages from their GitHub repositories.

Step 4.1: Download opencv from Github

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git clone https://github.com/opencv/opencv.git
cd opencv
git checkout 3.3.1
cd ..

Step 4.2: Download opencv_contrib from Github

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git clone https://github.com/opencv/opencv_contrib.git
cd opencv_contrib
git checkout 3.3.1
cd ..

Step 5: Compile and install OpenCV with contrib modules

Step 5.1: Create a build directory

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cd opencv
mkdir build
cd build

Step 5.2: Run CMake

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cmake -D CMAKE_BUILD_TYPE=RELEASE \
      -D CMAKE_INSTALL_PREFIX=/usr/local \
      -D INSTALL_C_EXAMPLES=ON \
      -D INSTALL_PYTHON_EXAMPLES=ON \
      -D WITH_TBB=ON \
      -D WITH_V4L=ON \
      -D WITH_QT=ON \
      -D WITH_OPENGL=ON \
      -D OPENCV_EXTRA_MODULES_PATH=../../opencv_contrib/modules \
      -D BUILD_EXAMPLES=ON ..

Step 5.3: Compile and Install

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# find out number of CPU cores in your machine
nproc
# substitute 4 by output of nproc
make -j4
sudo make install
sudo sh -c 'echo "/usr/local/lib" >> /etc/ld.so.conf.d/opencv.conf'
sudo ldconfig

Step 5.4: Create symlink in virtual environment

Depending upon Python version you have, paths would be different. OpenCV’s Python binary (cv2.so) can be installed either in directory site-packages or dist-packages. Use the following command to find out the correct location on your machine.

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find /usr/local/lib/ -type f -name "cv2*.so"

It should output paths similar to one of these (or two in case OpenCV was compiled for both Python2 and Python3):

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############ For Python 2 ############
## binary installed in dist-packages
/usr/local/lib/python2.6/dist-packages/cv2.so
/usr/local/lib/python2.7/dist-packages/cv2.so
## binary installed in site-packages
/usr/local/lib/python2.6/site-packages/cv2.so
/usr/local/lib/python2.7/site-packages/cv2.so
 
############ For Python 3 ############
## binary installed in dist-packages
/usr/local/lib/python3.5/dist-packages/cv2.cpython-35m-x86_64-linux-gnu.so
/usr/local/lib/python3.6/dist-packages/cv2.cpython-36m-x86_64-linux-gnu.so
## binary installed in site-packages
/usr/local/lib/python3.5/site-packages/cv2.cpython-35m-x86_64-linux-gnu.so
/usr/local/lib/python3.6/site-packages/cv2.cpython-36m-x86_64-linux-gnu.so

Double check the exact path on your machine before running the following commands

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############ For Python 2 ############
cd ~/.virtualenvs/facecourse-py2/lib/python2.7/site-packages
ln -s /usr/local/lib/python2.7/dist-packages/cv2.so cv2.so
 
############ For Python 3 ############
cd ~/.virtualenvs/facecourse-py3/lib/python3.6/site-packages
ln -s /usr/local/lib/python3.6/dist-packages/cv2.cpython-36m-x86_64-linux-gnu.so cv2.so

Step 6: Test OpenCV3

We will test a red eye remover application written in OpenCV to test our C++ and Python installations. Download RedEyeRemover.zip and extract it into a folder.

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