.. _Linux_Eclipse_Usage:

Using OpenCV with Eclipse (plugin CDT)
****************************************

.. note::
   Two ways, one by forming a project directly, and another by CMake

Prerequisites
===============

1. Having installed `Eclipse <http://www.eclipse.org/>`_ in your workstation (only the CDT plugin for C/C++ is needed). You can follow the following steps:

   * Go to the Eclipse site

   * Download `Eclipse IDE for C/C++ Developers <http://www.eclipse.org/downloads/packages/eclipse-ide-cc-developers/heliossr2>`_ . Choose the link according to your workstation.

#. Having installed OpenCV. If not yet, go :ref:`here <Linux-Installation>`.

Making a project
=================

1. Start Eclipse. Just run the executable that comes in the folder.

#. Go to **File -> New -> C/C++ Project**

   .. image:: images/a0.png
      :alt: Eclipse Tutorial Screenshot 0
      :align: center

#. Choose a name for your project (i.e. DisplayImage). An **Empty Project** should be okay for this example.

   .. image:: images/a1.png
      :alt: Eclipse Tutorial Screenshot 1
      :align: center

#. Leave everything else by default. Press **Finish**.

#. Your project (in this case DisplayImage) should appear in the **Project Navigator** (usually at the left side of your window).

   .. image:: images/a3.png
      :alt: Eclipse Tutorial Screenshot 3
      :align: center


#. Now, let's add a source file using OpenCV:

   * Right click on **DisplayImage** (in the Navigator). **New -> Folder** .

     .. image:: images/a4.png
        :alt: Eclipse Tutorial Screenshot 4
        :align: center

   * Name your folder **src** and then hit **Finish**

   * Right click on your newly created **src** folder. Choose **New source file**:

   * Call it **DisplayImage.cpp**. Hit **Finish**

     .. image:: images/a7.png
        :alt: Eclipse Tutorial Screenshot 7
        :align: center

#. So, now you have a project with a empty .cpp file. Let's fill it with some sample code (in other words, copy and paste the snippet below):

   .. code-block:: cpp

      #include <opencv2/opencv.hpp>

      using namespace cv;

      int main( int argc, char** argv )
      {
        Mat image;
        image = imread( argv[1], 1 );

        if( argc != 2 || !image.data )
          {
            printf( "No image data \n" );
            return -1;
          }

        namedWindow( "Display Image", WINDOW_AUTOSIZE );
        imshow( "Display Image", image );

        waitKey(0);

        return 0;
      }

#. We are only missing one final step: To tell OpenCV where the OpenCV headers and libraries are. For this, do the following:

    * Go to  **Project-->Properties**

    * In **C/C++ Build**, click on **Settings**. At the right, choose the **Tool Settings** Tab. Here we will enter the headers and libraries info:

      a. In **GCC C++ Compiler**, go to **Includes**. In **Include paths(-l)** you should include the path of the folder where opencv was installed. In our example, this is ``/usr/local/include/opencv``.

         .. image:: images/a9.png
            :alt: Eclipse Tutorial Screenshot 9
            :align: center

         .. note::
            If you do not know where your opencv files are, open the **Terminal** and type:

            .. code-block:: bash

               pkg-config --cflags opencv

            For instance, that command gave me this output:

            .. code-block:: bash

               -I/usr/local/include/opencv -I/usr/local/include


      b. Now go to **GCC C++ Linker**,there you have to fill two spaces:

         First in **Library search path (-L)** you have to write the path to where the opencv libraries reside, in my case the path is:
         ::

            /usr/local/lib

         Then in **Libraries(-l)** add the OpenCV libraries that you may need. Usually just the 3 first on the list below are enough (for simple applications) . In my case, I am putting all of them since I plan to use the whole bunch:


         opencv_core
         opencv_imgproc
         opencv_highgui
         opencv_ml
         opencv_video
         opencv_features2d
         opencv_calib3d
         opencv_objdetect
         opencv_contrib
         opencv_legacy
         opencv_flann

         .. image:: images/a10.png
             :alt: Eclipse Tutorial Screenshot 10
             :align: center

         If you don't know where your libraries are (or you are just psychotic and want to make sure the path is fine), type in **Terminal**:

         .. code-block:: bash

            pkg-config --libs opencv


         My output (in case you want to check) was:
         .. code-block:: bash

            -L/usr/local/lib -lopencv_core -lopencv_imgproc -lopencv_highgui -lopencv_ml -lopencv_video -lopencv_features2d -lopencv_calib3d -lopencv_objdetect -lopencv_contrib -lopencv_legacy -lopencv_flann

         Now you are done. Click **OK**

    * Your project should be ready to be built. For this, go to **Project->Build all**

      In the Console you should get something like

      .. image:: images/a12.png
         :alt: Eclipse Tutorial Screenshot 12
         :align: center

      If you check in your folder, there should be an executable there.

Running the executable
========================

So, now we have an executable ready to run. If we were to use the Terminal, we would probably do something like:

.. code-block:: bash

   cd <DisplayImage_directory>
   cd src
   ./DisplayImage ../images/HappyLittleFish.png

Assuming that the image to use as the argument would be located in <DisplayImage_directory>/images/HappyLittleFish.png. We can still do this, but let's do it from Eclipse:


#. Go to **Run->Run Configurations**

#. Under C/C++ Application you will see the name of your executable + Debug (if not, click over C/C++ Application a couple of times). Select the name (in this case **DisplayImage Debug**).

#. Now, in the right side of the window, choose the **Arguments** Tab. Write the path of the image file we want to open (path relative to the workspace/DisplayImage folder). Let's use **HappyLittleFish.png**:

   .. image:: images/a14.png
      :alt: Eclipse Tutorial Screenshot 14
      :align: center

#. Click on the **Apply** button and then in Run. An OpenCV window should pop up with the fish image (or whatever you used).

   .. image:: images/a15.jpg
      :alt: Eclipse Tutorial Screenshot 15
      :align: center

#. Congratulations! You are ready to have fun with OpenCV using Eclipse.

==================================================
V2: Using CMake+OpenCV with Eclipse (plugin CDT)
==================================================

Say you have or create a new file, *helloworld.cpp* in a directory called *foo*:

.. code-block:: cpp


   #include <opencv2/opencv.hpp>
   using namespace cv;

   int main ( int argc, char **argv )
   {
     Mat img(480, 640, CV_8U);
     putText(img, "Hello World!", Point( 200, 400 ), FONT_HERSHEY_SIMPLEX | FONT_ITALIC, 1.0, Scalar( 255, 255, 0 ));
     imshow("My Window", img);
     waitKey();
     return 0;
   }

1. Create a build directory, say, under *foo*: ``mkdir /build``.  Then ``cd build``.

#. Put a *CmakeLists.txt* file in build:

.. code-block:: bash

   PROJECT( helloworld_proj )
   FIND_PACKAGE( OpenCV REQUIRED )
   ADD_EXECUTABLE( helloworld helloworld.cxx )
   TARGET_LINK_LIBRARIES( helloworld ${OpenCV_LIBS} )

#. Run: ``cmake-gui ..`` and make sure you fill in where opencv was built.

#. Then click ``configure`` and then ``generate``. If it's OK, **quit cmake-gui**

#. Run ``make -j4``   *(the ``-j4`` is optional, it just tells the compiler to build in 4 threads)*. Make sure it builds.

#. Start ``eclipse`` . Put the workspace in some directory but **not** in ``foo`` or ``foo\\build``

#. Right click in the ``Project Explorer`` section. Select ``Import``  And then open the ``C/C++`` filter. Choose *Existing Code* as a Makefile Project``

#. Name your project, say *helloworld*. Browse to the Existing Code location ``foo\\build`` (where you ran your cmake-gui from). Select *Linux GCC* in the *"Toolchain for Indexer Settings"* and press *Finish*.

#. Right click in the ``Project Explorer`` section. Select ``Properties``. Under ``C/C++ Build``, set the *build directory:* from something like ``${workspace_loc:/helloworld}`` to ``${workspace_loc:/helloworld}/build`` since that's where you are building to.

 a. You can also optionally modify the ``Build command:`` from ``make`` to something like ``make VERBOSE=1 -j4`` which tells the compiler to produce detailed symbol files for debugging and also to compile in 4 parallel threads.

#. Done!