linux_gcc_cmake.rst



Using OpenCV with gcc and CMake

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):
No need to change anything when porting between Linux and Windows
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], 1 );

    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 2.8)
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: