Undefined reference to cv::imread(cv::String const&, int) [duplicate]

Question

I am trying to use OpenCV to write a simple code but I am not able to compile it successfully. Below is the code :

#include <iostream>
#include <stdio.h>
#include "opencv2/core/core.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"

using namespace std;
using namespace cv;

int main()
{
    Mat img = imread("insignia.jpg", -1);
    return 0;
}

and it won't work. Below is the error message I received.

/tmp/ccEMHPHa.o: In function `main':
main.cpp:(.text+0x46): undefined reference to `cv::imread(cv::String const&, int)'
/tmp/ccEMHPHa.o: In function `cv::String::String(char const*)':
main.cpp:(.text._ZN2cv6StringC2EPKc[_ZN2cv6StringC5EPKc]+0x58): undefined reference to `cv::String::allocate(unsigned long)'
/tmp/ccEMHPHa.o: In function `cv::String::~String()':
main.cpp:(.text._ZN2cv6StringD2Ev[_ZN2cv6StringD5Ev]+0x14): undefined reference to `cv::String::deallocate()'
/tmp/ccEMHPHa.o: In function `cv::Mat::~Mat()':
main.cpp:(.text._ZN2cv3MatD2Ev[_ZN2cv3MatD5Ev]+0x39): undefined reference to `cv::fastFree(void*)'
/tmp/ccEMHPHa.o: In function `cv::Mat::release()':
main.cpp:(.text._ZN2cv3Mat7releaseEv[_ZN2cv3Mat7releaseEv]+0x4b): undefined reference to `cv::Mat::deallocate()'
collect2: error: ld returned 1 exit status

I've tried searching for this issue online, but most of the answers didn't solve my problem. Can someone please help me?

Answer 1

This sounds like a problem with linking. I could compile your code without problems using g++:

g++ Test.cpp -L/path/to/my/openCV/lib -lopencv_core -lopencv_imgcodecs -o Test

If you want to use further functions of Open CV you might have to link against additional Open CV libraries.