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# 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):
  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], 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 )
    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:

## Help and Feedback

You did not find what you were looking for?

- Ask a question on the Q&A forum.
- If you think something is missing or wrong in the documentation, please file a bug report.

### Navigation

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- OpenCV 2.4.12.3 documentation »
- OpenCV Tutorials »
- Introduction to OpenCV »