Opencv_contrib: Building aruco samples from opencv_contrib_modules

[forestmaster]

Hey there, I've got a problem building aruco sample applications.
Hers what i've done so far:
I'downloaded opencv and the opencv_contrib-master, installed all the dependencies as they said on the opencv website:
sudo apt-get install build-essential
sudo apt-get install cmake git libgtk2.0-dev pkg-config libavcodec-dev libavformat-dev libswscale-dev
sudo apt-get install python-dev python-numpy libtbb2 libtbb-dev libjpeg-dev libpng-dev libtiff-dev libjasper-dev libdc1394-22-dev

Then I Iset up the build process for opencv with ccmake and specified the OPENCV_EXTRA_MODULES_PATH pointing to the contrib modules
then I compiled everything and ran sudo make install (without errors)

Now when I go to ~/opencv/opencv_contrib-master/modules/aruco, create a build directory and try to run ccmake, it gives the error:
(ocv_define_module): Unknown CMake command "ocv_define_module".
[and the warning that a lines is missing whichs defines the minimum required version... which I could eliminate by adding: "cmake_minimum_required(VERSION 2.8)" at the top of the file ]

the content of the cmakelits.txt in the /opencv_contrib-master/modules/aruco folder is only the two lines:
set(the_description "ArUco Marker Detection")
ocv_define_module(aruco opencv_core opencv_imgproc opencv_calib3d WRAP python)

has anyone experienced the same problem and could help me? I'm stuck here for days...
thank you very much!
Regards

[alalek]

You can't build only aruco module at this moment (these modules are not standalone).
You need to build whole OpenCV with additional contrib modules.

[forestmaster]

thanks for your answer, I built the whole OpenCV with the modules (I set the extra_modules_path variable).
My question was a misleading, sorry (I'm new to software development under linux...)

What I want to do is to change one of the samples (namely: detect_board.cpp) in the [...]/opencv_contrib-master/modules/aruco folder and compile it without having to compile everything again. So how can I take this example out and work on it seperatly?
By seperately I mean that I copy it out into an new folder structure and build this example seperately with an extra cmake file, not building whole opencv again.

[alalek]

Take a look here: https://github.com/Itseez/opencv/tree/master/samples/cpp/example_cmake
You need to point to OpenCV binary directory via OpenCV_DIR CMake variable (or via CMAKE_PREFIX_PATH to installation directory).

[forestmaster]

Now I got it! 'm able to build the (modified) example application.
Thank you very much!

[JeffBail]

To build the examples all you have to do is turn on the BUILD_EXAMPLES option when you build opencv_contrib. See the following in the README:

If you also want to build the samples from the "samples" folder of each module, also include the "-DBUILD_EXAMPLES=ON" option.