OpenCV 3.1.0 with Python 3.5

Question

After following several different tutorials, guides and steps recommended in other SO answers I didn't manage to install OpenCV for use with Python 3.5 in my Ubuntu 16.04 system.

As long as OpenCV 3.1.0 officially supports Python 3.x, how do I install it appropriately?

Answer 1

I managed installing Python 3.5 and OpenCV library appropriately in my system after gathering steps and troubleshooting solutions over different tutorials and guides.

The installation is performed under a virtualenv, so there is no need to clean up previous install attempts footprints from your system.

Following the steps presented here you'll install:

• openCV 3.1.0
• opencv_contrib 3.1.0
• numpy
• scipy
• scikit
• matplotlib
• cython
• venv

At the end, it may take up to 20Gb of space if you haven't already installed any of those packages previously.

You will need gcc-4.9+ for compiling OpenCV, I tested it with gcc-5.4

Install OpenCV dependencies

sudo apt-get build-dep -y opencv

Create and setup a virtualenv

sudo apt-get install python3-venv
python3.5 -m venv python35-opencv31
source ~/python35-opencv31/bin/activate
pip install matplotlib
pip install numpy
pip install scipy
pip install scikit-learn
pip install cython
pip install -U scikit-image

Compile OpenCV 3.1.0 and openvc_contrib 3.1.0

Dependencies

sudo apt-get install build-essential cmake libgtk2.0-dev pkg-config libavcodec-dev libavformat-dev libswscale-dev libtbb2 libtbb-dev libjpeg-dev libpng-dev libtiff-dev libjasper-dev libdc1394-22-dev

Getting repositories

mkdir ~/git
cd ~/git
git clone https://github.com/opencv/opencv.git
cd ./opencv
git checkout 3.1.0

cd ~/git
git clone https://github.com/Itseez/opencv_contrib.git
cd ./opencv_contrib
git checkout 3.1.0

Making sure some libs will be found

ffmpeg libs

sudo -i
mkdir /usr/include/ffmpeg
cd /usr/include/ffmpeg
ln -sf /usr/include/x86_64-linux-gnu/libavcodec/*.h ./
ln -sf /usr/include/x86_64-linux-gnu/libavformat/*.h ./
ln -sf /usr/include/x86_64-linux-gnu/libswscale/*.h ./

If, during compilation, occurs any problems when trying to find some ffmpeg libs, uninstall ffmpeg and build it from source.

python bindings with opencv_contrib modules

echo "\nfind_package(HDF5)\ninclude_directories(\${HDF5_INCLUDE_DIRS})" >> ~/git/opencv/modules/python/common.cmake

Compiling

source ~/python35-opencv31/bin/activate
mkdir ~/opencv3.1.0
cd ~/git/opencv/
mkdir release
cd ./release
export CC=$(which gcc)
export CXX=$(which g++)
cmake -D CMAKE_BUILD_TYPE=RELEASE \
    -D CMAKE_INSTALL_PREFIX=~/opencv3.1.0 \
    -D INSTALL_C_EXAMPLES=OFF \
    -D INSTALL_PYTHON_EXAMPLES=ON \
    -D OPENCV_EXTRA_MODULES_PATH=~/git/opencv_contrib/modules \
    -D BUILD_EXAMPLES=ON \
    -D CUDA_NVCC_FLAGS="-D_FORCE_INLINES" ..

The output should include this:

--   Python 2:
--     Interpreter:                 /home/rodrigo/anaconda/bin/python2.7 (ver 2.7.12)
--     Libraries:                   /usr/lib/x86_64-linux-gnu/libpython2.7.so (ver 2.7.12)
--     numpy:                       /home/rodrigo/anaconda/lib/python2.7/site-packages/numpy/core/include (ver 1.10.4)
--     packages path:               lib/python2.7/site-packages
-- 
--   Python 3:
--     Interpreter:                 /home/rodrigo/python35-opencv/bin/python3 (ver 3.5.2)
--     Libraries:                   /usr/lib/x86_64-linux-gnu/libpython3.5m.so (ver 3.5.2)
--     numpy:                       /home/rodrigo/python35-opencv/lib/python3.5/site-packages/numpy/core/include (ver 1.11.2)
--     packages path:               lib/python3.5/site-packages
-- 
--   Python (for build):            /home/rodrigo/anaconda/bin/python2.7

Now:

make

If it succeed, then:

make install

Add OpenCV libs to your virtualenv

cd ~/python35-opencv31/lib/site-packages
ln -s ~/opencv3.1.0/lib/python3.5/site-packages/cv2.cpython-35m-x86_64-linux-gnu.so

Done!

To test if it works as expected:

cd ~
source ~/python35-opencv31/bin/activate
python
import cv2
cv2.__version__

It should import cv2 and show version number 3.1.0.