In this post we will see How to Install OpenCV in Ubuntu for C/C++
OpenCV is an image processing library created by Intel and later supported by Willow Garage and now maintained by Itseez. OpenCV means Intel® Open Source Computer Vision Library. It is a collection of C functions and a few C++ classes that implement some popular Image Processing and Computer Vision algorithms. OpenCV is Available on Mac, Windows, Linux (Terminal environment).

Step 1 – Updating Ubuntu

$ sudo apt-get update

$ sudo apt-get upgrade

Step 2 – Install dependencies

$ sudo apt-get install build-essential cmake git libgtk2.0-dev pkg-config libavcodec-dev libavformat-dev libswscale-dev

$ sudo apt-get install python3.5-dev python3-numpy libtbb2 libtbb-dev

$ sudo apt-get install libjpeg-dev libpng-dev libtiff5-dev libjasper-dev libdc1394-22-dev libeigen3-dev libtheora-dev libvorbis-dev libxvidcore-dev libx264-dev sphinx-common libtbb-dev yasm libfaac-dev libopencore-amrnb-dev libopencore-amrwb-dev libopenexr-dev libgstreamer-plugins-base1.0-dev libavutil-dev libavfilter-dev libavresample-dev

Step 3 –  Get OpenCV

$ sudo -s

$ cd /opt

/opt$ git clone https://github.com/Itseez/opencv.git

/opt$ git clone https://github.com/Itseez/opencv_contrib.git

Step 4 – build and install OpenCV

/opt$ cd opencv

/opt/opencv$ mkdir release

/opt/opencv$ cd release

/opt/opencv/release$ cmake -D BUILD_TIFF=ON -D WITH_CUDA=OFF -D ENABLE_AVX=OFF -D WITH_OPENGL=OFF -D WITH_OPENCL=OFF -D WITH_IPP=OFF -D WITH_TBB=ON -D BUILD_TBB=ON -D WITH_EIGEN=OFF -D WITH_V4L=OFF -D WITH_VTK=OFF -D BUILD_TESTS=OFF -D BUILD_PERF_TESTS=OFF -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local -D OPENCV_EXTRA_MODULES_PATH=/opt/opencv_contrib/modules /opt/opencv/

/opt/opencv/release$ make -j4

/opt/opencv/release$ make install

/opt/opencv/release$ ldconfig

/opt/opencv/release$ exit

/opt/opencv/release$ cd ~

Now to check if OpenCV is installed on a machine, run the following commands

$ pkg-config --modversion opencv
3.2.x

We will get the opencv version installed
in this case it’s 3.2.x

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Create a C++ program

Follow the commands

$ mkdir cpp_test

$ cd cpp_test

$ touch main.cpp

The above command will create a folder called cpp_test and create a main.cpp file inside it
Now place any .jpeg image inside the cpp_test folder.
So Now your cpp_test folder will contain two files as follows
.
├── sample.jpeg
└── main.cpp

Now open the main.cpp and add the following code

#include <opencv2/highgui.hpp>
#include <iostream>

int main( int argc, char** argv ) {
  
  cv::Mat image;
  image = cv::imread("sample.jpeg" , CV_LOAD_IMAGE_COLOR);
  
  if(! image.data ) {
      std::cout <<  "Could not open or find the image" << std::endl ;
      return -1;
    }
  
  cv::namedWindow( "Display window", cv::WINDOW_AUTOSIZE );
  cv::imshow( "Display window", image );
  
  cv::waitKey(0);
  return 0;
}

Now compile your code with the following command

g++ main.cpp -o output `pkg-config --cflags --libs opencv`

Now run the C++ program with the following command

$ ./output

press ESC to exit

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Video instruction – How to Install OpenCV in Ubuntu 18.04 LTS for C / C++