OpenCV installation on Ubuntu 18.04

Install the OpenCV with versions of Python 2/3 and C++ on Ubuntu 18.04

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Preparations

# Update the package lists
sudo apt update -y

# Install required packages
sudo apt install -y pkg-config python-dev python-numpy python-scipy python-setuptools python-pip

Direct Installation

With Python 2

Input command:

sudo apt install python-opencv -y

Confirm a correct installation of OpenCV with Python 2:

$ python
Python 2.7.17 (default, Mar 18 2022, 13:21:42) 
[GCC 7.5.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import cv2
>>> cv2.__version__
'4.5.0'

With Python 3

Input command:

sudo apt install python3-opencv -y

Confirm a correct installation of OpenCV with Python 3:

$ python3
Python 3.6.9 (default, Mar 15 2022, 13:55:28) 
[GCC 8.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import cv2
>>> cv2.__version__
'4.6.0'

With C++

Input command:

sudo apt install libopencv-dev -y

Confirm a correct installation of OpenCV with C++:

$ pkg-config --modversion opencv
3.2.0

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Sources Building

Install the required packages to build the official sources

sudo apt-get install -y cmake git libgtk2.0-dev pkg-config  mlocate \ 
libavcodec-dev libavformat-dev libswscale-dev libtbb2 libtbb-dev libjpeg-dev \
libpng-dev libtiff-dev libjasper1 libjasper-dev libdc1394-22-dev build-essential

Download sources from OpenCV website

# Go to $HOME folder
cd ~

# 4.6.0 was released on June 12, 2022
wget -O opencv.zip https://github.com/opencv/opencv/archive/4.6.0.zip
wget -O opencv_contrib.zip https://github.com/opencv/opencv_contrib/archive/4.6.0.zip

# Unzip the folder of sources
unzip opencv.zip
unzip opencv_contrib.zip

# Do operations for working folders
mv opencv-4.5.0 opencv
mv opencv_contrib-4.5.0 opencv_contrib
mv opencv_contrib opencv
cd ~/opencv && mkdir build && cd build

Build all

It will take long time to build all, but you can speed it up by {-jN}: N is as twice as the number of kernels of your CPU.

cmake ..
sudo make -j8 
sudo make install
cd ~
rm opencv.zip opencv_contrib.zip

Config the path of OpenCV libraries

sudo touch /etc/ld.so.conf.d/opencv.conf
sudo echo "/usr/local/lib" >> /etc/ld.so.conf.d/opencv.conf
sudo ldconfig
sudo echo "PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/lib/pkgconfig" >> /etc/bash.bashrc
sudo echo "export PKG_CONFIG_PATH" >> /etc/bash.bashrc
source /etc/bash.bashrc
sudo updatedb -y

Restart the computer if required

sudo reboot

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Additional Environment Setup (If Required)

Reading multimedia data from OpenCV samples

echo "export OPENCV_SAMPLES_DATA_PATH=~/opencv/samples/data" >> ~/.bashrc
source ~/.bashrc

Allow Ubuntu 18.04 to decode mpeg-4 formats

sudo apt-get install ubuntu-restricted-extras
sudo apt-get install libavcodec54 libav-tools ffmpeg