Using OpenCV with gcc and CMake#

Original author

Ana Huamán

Compatibility

OpenCV >= 3.0

Warning

This tutorial can contain obsolete information.

Note

We assume that you have successfully installed OpenCV in your workstation.

  • The easiest way of using OpenCV in your code is to use CMake. A few advantages (taken from the Wiki):

    1. No need to change anything when porting between Linux and Windows

    2. Can easily be combined with other tools by CMake( i.e. Qt, ITK and VTK )

  • If you are not familiar with CMake, checkout the tutorial on its website.

Steps#

Create a program using OpenCV#

Let’s use a simple program such as DisplayImage.cpp shown below.

#include <stdio.h>
#include <opencv2/opencv.hpp>

using namespace cv;

int main(int argc, char** argv )
{
    if ( argc != 2 )
    {
        printf("usage: DisplayImage.out <Image_Path>\n");
        return -1;
    }

    Mat image;
    image = imread( argv[1], IMREAD_COLOR );

    if ( !image.data )
    {
        printf("No image data \n");
        return -1;
    }
    namedWindow("Display Image", WINDOW_AUTOSIZE );
    imshow("Display Image", image);

    waitKey(0);

    return 0;
}

Create a CMake file#

Now you have to create your CMakeLists.txt file. It should look like this:

cmake_minimum_required(VERSION 3.13)
project( DisplayImage )
find_package( OpenCV REQUIRED )
include_directories( ${OpenCV_INCLUDE_DIRS} )
add_executable( DisplayImage DisplayImage.cpp )
target_link_libraries( DisplayImage ${OpenCV_LIBS} )

Generate the executable#

This part is easy, just proceed as with any other project using CMake:

cd <DisplayImage_directory>
cmake .
make

Result#

By now you should have an executable (called DisplayImage in this case). You just have to run it giving an image location as an argument, i.e.:

./DisplayImage lena.jpg

You should get a nice window as the one shown below: