Compile and link OpenCV to my project in my main CMakeLists.txt

I am new to cmake. I have a project which uses dlib and opencv. They are defined as submodules which are in third_party folder. I want to link them to my main project which is 'node' with cmake but I could not achieved. I am sharing my project tree. I did with find_package(OpenCV) and target_link_libraries(recognition-node ${OPENCV_LIBS}) way but I need to compile from source without installing anything. At last, I just want to write 'cmake . && make'

.
├── CMakeLists.txt
├── node
│   ├── build.sh
│   ├── CMakeLists.txt
│   ├── configure.sh
│   ├── findfacestask.cpp
│   ├── findfacestask.h
│   ├── main.cpp
│   ├── matrixwrapper.h
│   ├── poolcontext.cpp
│   ├── poolcontext.h
│   ├── recognition.dat
│   ├── recognizefacetask.cpp
│   ├── recognizefacetask.h
│   ├── runscript
│   ├── sp.dat
│   ├── task.cpp
│   ├── task.h
│   ├── unhandledexception.cpp
│   ├── unhandledexception.h
│   ├── webcamfeed.cpp
│   ├── webcamfeed.h
│   ├── wrapper.cpp
│   └── wrapper.h
└── third_party
    ├── dlib
    │   ├── appveyor.yml
    │   ├── CMakeLists.txt
    │   ├── dlib
    │   ├── docs
    │   ├── examples
    │   ├── MANIFEST.in
    │   ├── python_examples
    │   ├── README.md
    │   ├── setup.py
    │   └── tools
    └── opencv
        ├── 3rdparty
        ├── apps
        ├── cmake
        ├── CMakeLists.txt
        ├── CONTRIBUTING.md
        ├── data
        ├── doc
        ├── include
        ├── LICENSE
        ├── modules
        ├── platforms
        ├── README.md
        └── samples

Content of my top CMakeLists.txt

cmake_minimum_required(VERSION 2.8.12)

set (CMAKE_CXX_STANDARD 11)

add_subdirectory(node)
add_subdirectory(third_party/dlib)
add_subdirectory(third_party/opencv)

Content of node/CMakeLists.txt

cmake_minimum_required(VERSION 2.8.12)
project(recognition-node)

set(CMAKE_AUTOMOC ON)

find_package(Qt5Widgets REQUIRED)

add_executable(recognition-node main.cpp  
            webcamfeed.cpp 
            poolcontext.cpp 
            unhandledexception.cpp
            task.cpp
            findfacestask.cpp
            wrapper.cpp
            recognizefacetask.cpp)

target_link_libraries(recognition-node Qt5::Widgets)
target_link_libraries(recognition-node dlib::dlib)
target_link_libraries(recognition-node opencv::core)

It gives error in 'make' stage which is :

/home/arnes/workspace/recognition-node/node/poolcontext.h:10:28: fatal error: 
opencv2/core.hpp: No such file or directory

Solution

Since you insist on keeping the opencv in your project tree

It is easier way but I just want it to do in this way.

Here is the solution that for sure works fine with your project tree that you posted in the question and with opencv-3.4.1. For simplicity I will neglect dlib library and Qt dependency, since you didn't have any problem with it.

Root CMakeLists.txt should have the following content:

cmake_minimum_required(VERSION 2.8.11) # or anything higher, if you wish
project(recognition-node CXX)

add_subdirectory(node)

The CMakeLists.txt under the node directory should have the following content:

add_subdirectory(third_party)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -g") # or any other additional flags

# at this point you can add find_package(Qt5Widgets REQUIRED) and later link your binary against Qt5::widgets as well
add_executable(myExec main.cpp
# and put here all the other source files of your project ...
)
# for linking libs I have put additionally highgui and imgproc to check the solution against OpenCV official sample
target_link_libraries(myExec opencv_core opencv_highgui opencv_imgproc)

target_include_directories(myExec PUBLIC 
    third_party/opencv/modules/calib3d/include
    third_party/opencv/modules/core/include
    third_party/opencv/modules/cudaarithm/include
    third_party/opencv/modules/cudabgsegm/include
    third_party/opencv/modules/cudacodec/include
    third_party/opencv/modules/cudafeatures2d/include
    third_party/opencv/modules/cudafilters/include
    third_party/opencv/modules/cudaimgproc/include
    third_party/opencv/modules/cudalegacy/include
    third_party/opencv/modules/cudaobjdetect/include
    third_party/opencv/modules/cudaoptflow/include
    third_party/opencv/modules/cudastereo/include
    third_party/opencv/modules/cudawarping/include
    third_party/opencv/modules/cudev/include
    third_party/opencv/modules/dnn/include
    third_party/opencv/modules/features2d/include
    third_party/opencv/modules/flann/include
    third_party/opencv/modules/highgui/include
    third_party/opencv/modules/imgcodecs/include
    third_party/opencv/modules/imgproc/include
    third_party/opencv/modules/ml/include
    third_party/opencv/modules/objdetect/include
    third_party/opencv/modules/photo/include
    third_party/opencv/modules/shape/include
    third_party/opencv/modules/stitching/include
    third_party/opencv/modules/superres/include
    third_party/opencv/modules/ts/include
    third_party/opencv/modules/video/include
    third_party/opencv/modules/videoio/include
    third_party/opencv/modules/videostab/include
    third_party/opencv/modules/viz/include
    third_party/opencv/modules/world/include
)

The CMakeLists.txt under third_party should contain only:

add_subdirectory(opencv)
# add_subdirectory(dlib) # if you will use dlib, of course also add dlib

The sample I used to verify the build is contours2.cpp (just copy pasted the content into main.cpp).

However, I still think that it is a terrible idea to use this solution.

OpenCv takes really a lot of time to compile
you have to manually add include dirs (you can use some macro generators, but usually it looks even more ugly)
in your build system you have a lot of targets (over 300) that you don't really need, including install target

So, my recommendation is: if you want, use this solution for scientific purpose, but just compile and install OpenCv system-wise (or locally, if you are not the admin) when you really need to use it.