How do I add OpenCV to LD_LIBRARY path in linux? - c++

Question

I used this link to install OpenCV.
What works:
1.OpenCV works fine with python (running from terminal).
2.I can import opencv libraries in a single C++ program.
What does not work :
When the code is spread across multiple and you need to build it using CMake.
Here's my CmakeLists.txt :
1.cmake_minimum_required(VERSION 3.9)
2.project(Image_processing)
3.set(CMAKE_CXX_STANDARD 14)
4.find_package(OpenCV REQUIRED)
5.include_directories(/home/user/opencv/build)
6.add_executable(main main.cpp)
7.target_link_libraries(project_name ${OpenCV_LIBS})
Errors (can regenerate them by commenting lines 4,5 and 7 in above CMake file):
undefined reference to OpenCV functions.
CMake Error at CMakeLists.txt:7 (target_link_libraries):
Cannot specify link libraries for target "Image_processing" which is not
built by this project.

Answer 1

Correct it with:
cmake_minimum_required(VERSION 3.5)
project(Image_processing)
set(CMAKE_CXX_STANDARD 14)
find_package(OpenCV REQUIRED)
include_directories(${OpenCV_INCLUDE_DIRS})
add_executable(main main.cpp)
target_link_libraries(main ${OpenCV_LIBS})

Answer 2

In your CMakeLists.txt, the exe-name is not matching with the target-link-name. I modify the line, then it works on my PC.
The CMakeLists.txt of an OpenCV Project:
cmake_minimum_required(VERSION 3.5)
project(Image_processing)
set(CMAKE_CXX_STANDARD 14)
find_package(OpenCV REQUIRED)
#include_directories(/home/user/opencv/build)
add_executable(Image_processing main.cpp)
target_link_libraries(Image_processing ${OpenCV_LIBS})