Install OpenCV 4 on Raspberry Pi. In this post, we will provide a bash script for installing OpenCV-4.0 (C++, Python 2.7 and Python 3.5) on Raspbian Operating System on Raspberry Pi. We will also briefly study the script to understand what’s going on in it.
Note that this script takes around 3 times more on Raspberry Pi 2 as compared to Raspberry Pi 3.
Step 0: Select OpenCV version to install
First let’s prepare the system for the installation.
sudo apt-get -y purge wolfram-engine sudo apt-get -y purge libreoffice* sudo apt-get -y clean sudo apt-get -y autoremove 
echo "OpenCV installation by learnOpenCV.com" cvVersion="masrer"
We are also going to clean build directories and create installation directory.
# Clean build directories rm -rf opencv/build rm -rf opencv_contrib/build # Create directory for installation mkdir installation mkdir installation/OpenCV-"$cvVersion" Finally, we will be storing the current working directory in cwd variable. We are also going to refer to this directory as OpenCV_Home_Dir throughout this article.
# Save current working directory cwd=$(pwd) Step 1: Update Packages
sudo apt -y update sudo apt -y upgrade Step 2: Install OS Libraries
sudo apt-get -y remove x264 libx264-dev ## Install dependencies sudo apt-get -y install build-essential checkinstall cmake pkg-config yasm sudo apt-get -y install git gfortran sudo apt-get -y install libjpeg8-dev libjasper-dev libpng12-dev sudo apt-get -y install libtiff5-dev sudo apt-get -y install libtiff-dev sudo apt-get -y install libavcodec-dev libavformat-dev libswscale-dev libdc1394-22-dev sudo apt-get -y install libxine2-dev libv4l-dev cd /usr/include/linux sudo ln -s -f ../libv4l1-videodev.h videodev.h cd $cwd sudo apt-get -y install libgstreamer0.10-dev libgstreamer-plugins-base0.10-dev sudo apt-get -y install libgtk2.0-dev libtbb-dev qt5-default sudo apt-get -y install libatlas-base-dev sudo apt-get -y install libmp3lame-dev libtheora-dev sudo apt-get -y install libvorbis-dev libxvidcore-dev libx264-dev sudo apt-get -y install libopencore-amrnb-dev libopencore-amrwb-dev sudo apt-get -y install libavresample-dev sudo apt-get -y install x264 v4l-utils # Optional dependencies sudo apt-get -y install libprotobuf-dev protobuf-compiler sudo apt-get -y install libgoogle-glog-dev libgflags-dev sudo apt-get -y install libgphoto2-dev libeigen3-dev libhdf5-dev doxygen Step 3: Install Python Libraries
sudo apt-get -y install python3-dev python3-pip sudo -H pip3 install -U pip numpy sudo apt-get -y install python3-testresources We are also going to install virtualenv and virtualenvwrapper modules to create Python virtual environments.
cd $cwd # Install virtual environment python3 -m venv OpenCV-"$cvVersion"-py3 echo "# Virtual Environment Wrapper" >> ~/.bashrc echo "alias workoncv-$cvVersion=\"source $cwd/OpenCV-$cvVersion-py3/bin/activate\"" >> ~/.bashrc source "$cwd"/OpenCV-"$cvVersion"-py3/bin/activate ############# Next, we create the Python virtual environment.
############ For Python 3 ############ # now install python libraries within this virtual environment sudo sed -i 's/CONF_SWAPSIZE=100/CONF_SWAPSIZE=1024/g' /etc/dphys-swapfile sudo /etc/init.d/dphys-swapfile stop sudo /etc/init.d/dphys-swapfile start pip install numpy dlib # quit virtual environment deactivate 
Step 4: Download opencv and opencv_contrib
git clone https://github.com/opencv/opencv.git cd opencv git checkout $cvVersion cd .. git clone https://github.com/opencv/opencv_contrib.git cd opencv_contrib git checkout $cvVersion cd .. Step 5: Compile and install OpenCV with contrib modules
First we navigate to the build directory.
cd opencv mkdir build cd build Next, we start the compilation and installation process.
cmake -D CMAKE_BUILD_TYPE=RELEASE \ -D CMAKE_INSTALL_PREFIX=$cwd/installation/OpenCV-"$cvVersion" \ -D INSTALL_C_EXAMPLES=ON \ -D INSTALL_PYTHON_EXAMPLES=ON \ -D WITH_TBB=ON \ -D WITH_V4L=ON \ -D OPENCV_PYTHON3_INSTALL_PATH=$cwd/OpenCV-$cvVersion-py3/lib/python3.5/site-packages \ -D WITH_QT=ON \ -D WITH_OPENGL=ON \ -D OPENCV_EXTRA_MODULES_PATH=../../opencv_contrib/modules \ -D BUILD_EXAMPLES=ON .. make -j$(nproc) make install Step 6: Reset swap file
Once we are done with installing heavy Python modules like Numpy, it’s time to reset the swap file.
sudo sed -i 's/CONF_SWAPSIZE=1024/CONF_SWAPSIZE=100/g' /etc/dphys-swapfile sudo /etc/init.d/dphys-swapfile stop sudo /etc/init.d/dphys-swapfile start Finally, we also need to add a simple statement to make sure that VideoCapture(0) works on our Raspberry Pi.
echo "sudo modprobe bcm2835-v4l2" >> ~/.profile How to use OpenCV in C++
There are two ways to use OpenCV in C++, the preferred way is to use CMake, the other one being command line compilation using g++. We will have a look at both ways.
Using CMakeLists.txt
The basic structure of your CMakeLists.txt will stay the same. Only difference being, that you will have to set OpenCV_DIR as shown below.
cmake_minimum_required(VERSION 3.1) # Enable C++11 set(CMAKE_CXX_STANDARD 11) set(CMAKE_CXX_STANDARD_REQUIRED TRUE) SET(OpenCV_DIR <OpenCV_Home_Dir>/installation/OpenCV-master/lib/cmake/opencv4) Make sure that you replace OpenCV_Home_Dir with correct path. For example, in my case:
SET(OpenCV_DIR /home/hp/OpenCV_installation/installation/OpenCV-master/lib/cmake/opencv4) Once you have made your CMakeLists.txt, follow the steps given below.
mkdir build && cd build cmake .. cmake --build . --config Release This will generate your executable file in build directory.
Using g++
To compile a sample file (let’s say my_sample_file.cpp), use the following command.
g++ `pkg-config --cflags --libs <OpenCV_Home_Dir>/installation/OpenCV-master/lib/pkgconfig/opencv.pc` my_sample_file.cpp -o my_sample_file How to use OpenCV in Python
To use the OpenCV version installed using Python script, first we activate the correct Python Virtual Environment.
For OpenCV-master : Python 3
workon OpenCV-master-py3 Once you have activated the virtual environment, you can enter Python shell and test OpenCV version.
ipython import cv2 print(cv2.__version__) Hope this script proves to be useful for you :). Stay tuned for more interesting stuff. In case of any queries, feel free to comment below and we will get back to you as soon as possible.
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