How To Install OpenCV4

How To Build OpenCV4 From Source On Linux

This uses some of the methods as presented by the openCV team. However, I skip some unnecessary steps for our use of OpenCV (aka installing it for C++ and Java). If for some reason the method doesn't setup properly come to me (Troake).

The original tutorial is available here

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First step is to ensure that we can build the source. Therefore some dependencies are required.

sudo apt-get install cmake
sudo apt-get install python-devel numpy
sudo apt-get install gcc gcc-c++

Cmake is used for building C applications. OpenCV is a C/C++ based library. It just also has Python support. In order to use extra features such as gstreamer, these dependencies must also be downloaded and installed:

sudo apt-get install gtk2-devel
sudo apt-get install libv4l-devel
sudo apt-get install ffmpeg-devel
sudo apt-get install gstreamer-plugins-base-devel

The source for OpenCV is on github so you have to clone the repository. Run this command in a location to hold the source.

git clone https://github.com/opencv/opencv.git

When you run the git clone, it will put it all in a folder called opencv in that directory. The next step is to make a directory for the built version of OpenCV. Go into the opencv folder and create a build folder.

cd opencv
mkdir build

Go into the build directory and run cmake on the parent directory.

cd build
cmake ../

(or you can just run cmake from the opencv folder)

cmake

You should get something like this close to the end of the cmake log. This confirms that OpenCV recognises Python 3 on the machine (There may also be some info about Python2. That's all good as long as you see the Python3 info).

--   Python 3:
--     Interpreter:                 /usr/bin/python3.4 (ver 3.4.3)
--     Libraries:                   /usr/lib/x86_64-linux-gnu/libpython3.4m.so (ver 3.4.3)
--     numpy:                       /usr/lib/python3/dist-packages/numpy/core/include (ver 1.8.2)
--     packages path:               lib/python3.4/dist-packages

After cmake is finished go into the /build/python_loader folder and run setup.py.

python3 setup.py install

How to install OpenCV4 on Windows

Windows is a little complicated for things like this but if you want to give it a try, check out this tutorial or follow the instructions below.

Get dependencies

Download and install Visual Studio Build Tools from here. When installing select Desktop development with C++.

Download and install CMake from here. When installing add it to your system path.

Download and install Python 3 form here.

Download and install git for Windows from here.

Install OpenCV4

Download the latest Win pack from https://opencv.org/releases.html

Run the downloaded executable and extract the contents to where you want the program to be installed.

As administrator then run:

$ setx -m OPENCV_DIR C:\OPENCVDIR\Build\x64\vc14

Where OPENCVDIR is the directory you extracted it to.

Then open the program Edit the system environmental variables, Environmental Variables... and add a new entry to the PATH being %OPENCV_DIR%\bin

To add python support go to the python directory opencv\build\python and run the following:

$ python setup.py install

Everything should now be installed and to check that things are working run:

$ python
>>> import cv2
>>> cv2.__version__

If it prints out '4.0.0' everything is good to go.