Using OpenCV with gcc and CMake {#tutorial_linux_gcc_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. @code{.cpp} #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;

} @endcode

Create a CMake file

Now you have to create your CMakeLists.txt file. It should look like this: @code{.cmake} 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} ) @endcode

Generate the executable

This part is easy, just proceed as with any other project using CMake: @code{.bash} cd <DisplayImage_directory> cmake . make @endcode

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.: @code{.bash} ./DisplayImage lena.jpg @endcode You should get a nice window as the one shown below: