# How to setup Qt and OpenCV 3.4.xx on Ubuntu 20.04

###### tags: `Linux`

> References: https://docs.opencv.org/4.x/db/df5/tutorial_linux_gcc_cmake.html https://shengyu7697.github.io/opencv-3-4-7-build-install-in-ubuntu/

## Make OpenCV with cmake
1. Install package for cmake

sudo apt-get install build-essential cmake

2. Download source from opencv offical github and unzip
https://github.com/opencv/opencv/tree/3.4.15
3. Compile opencv and install (Use opencv 3.4.15)

cd opencv-3.4.15 //file name is the version you download
mkdir -p build && cd build
cmake ..
make -j4
sudo make install
sudo ldconfig -v

4. Check if opencv is installed

$ opencv_version
3.4.15

## Qt CMakeLists.txt setup
1. Create QT project
`File -> New file or Project...`
2. Choose a template
3. Set **Define Bulid System** to **CMake**
4. After created project navigate to **CMakeLists.txt**
5. Append following scripts before `target_link_libraries(qt_cmake_test PRIVATE Qt${QT_VERSION_MAJOR}::Widgets)`

set(OpenCV_LIBS
    "opencv_calib3d"
    "opencv_core"
    "opencv_dnn"
    "opencv_features2d"
    "opencv_flann"
    "opencv_highgui"
    "opencv_imgcodecs"
    "opencv_imgproc"
    "opencv_ml"
    "opencv_objdetect"
    "opencv_photo"
    "opencv_shape"
    "opencv_stitching"
    "opencv_superres"
    "opencv_video"
    "opencv_videoio"
    "opencv_videostab"
)

set(OpenCV_INCLUDE_DIRS
    "/usr/local/include"
    "/usr/local/include/opencv"
)

5. Append `${OpenCV_LIBS}`

arget_link_libraries(qt_cmake_test PRIVATE Qt${QT_VERSION_MAJOR}::Widgets ${OpenCV_LIBS})

6. Append following scripts in the end

include_directories( ${OpenCV_INCLUDE_DIRS} )
message(STATUS ${OpenCV_LIBS})
message(STATUS ${OpenCV_INCLUDE_DIRS})

7. All done!