OpenCV cannot find libraries [duplicate] - c++

Question

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What is an undefined reference/unresolved external symbol error and how do I fix it?
(39 answers)
Closed 7 years ago.
I am trying to read an image in OpenCV, like this:
#include <opencv2/core/core.hpp>
#include <opencv2/imgcodecs.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/opencv.hpp>
using namespace cv;
using namespace std;
int main (int argv, char **argc)
{
Mat image = imread("Foam_Image.jg", CV_LOAD_IMAGE_GRAYSCALE);
return 0;
}
But I get the following error:
undefined reference to cv::imread(cv::String const&, int)
It seems that OpenCV cannot find the libraries I included, maybe because I didn't link them correctly, or maybe there are some libraries missing. Does anyone know how to look for missing libraries or how to link the libraries in OpenCV?

Answer 1

If your operating system is any UNIX which has CMake, then it would be better for you to write a CMakelists.txt file as follows
cmake_minimum_required(VERSION 2.8)
project( DisplayImage )
find_package( OpenCV REQUIRED )
add_executable( DisplayImage DisplayImage.cpp )
target_link_libraries( DisplayImage ${OpenCV_LIBS} )
And just use
cmake .
make
./DisplayImage
to execute the program.
you can install CMake from the official repositories using your package manager
In case your operating system is Windows, install CMake and set compiler options as Visual Studio (your version). Also add the OpenCV path to your system path, if not already done.
More instructions here :
http://docs.opencv.org/doc/tutorials/introduction/windows_install/windows_install.html