CODEWITHSUNDEEP
c++opencv
Felipe Machado
Felipe Machado

Reputation: 79

undefined reference to `cv::VideoCapture::VideoCapture(int)

i'm trying to use my webcam using C++ and OpenCV, but i'm gettin this error

(...):Images.cpp:(.text+0x27): undefined reference to cv::VideoCapture::VideoCapture(int)

(...):Images.cpp:(.text+0x38): undefined reference to cv::VideoCapture::~VideoCapture()

(...):Images.cpp:(.text$_ZN2cv6StringD1Ev[_ZN2cv6StringD1Ev]+0x11): undefined reference to cv::String::deallocate() ...

My code:

#include <iostream>
#include <string.h>
#include "opencv2/core/core.hpp"
#include "opencv2/opencv.hpp"
#include "opencv2/videoio/videoio.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/video.hpp"
#include "opencv2/imgproc/imgproc.hpp"

using namespace std;
using namespace cv;


int main(int argc, char const *argv[])
{
    VideoCapture cap(0);
    return 0;
}

Upvotes: 7

Views: 28897

Answers (4)

user889030
user889030

Reputation: 4754

you probably missing opencv libs , try to add them to your project config file like 

LIBS += -LC:\\opencv\\opeencv4.1\\x86\\mingw\\bin \
    libopencv_core410 \
    libopencv_highgui410 \
    libopencv_imgcodecs410 \
    libopencv_imgproc410 \
    libopencv_features2d410 \
    libopencv_video410 \
    libopencv_videoio410 \

Upvotes: 1

florian
florian

Reputation: 31

I had the same problem after forking a Github project. I resolved it using these posts.
My problem was in the Makefile I forked, I had to replace these lines. oldLine:

$(EXECUTABLE): $(OBJECTS)
        $(CC) $(LDFLAGS) $(OBJECTS) -o $@

newLine:

$(EXECUTABLE): $(OBJECTS)
        $(CC) $(OBJECTS) $(LDFLAGS) -o $@

I hope it can help someone ;)

Upvotes: 2

vishwanath_hugar
vishwanath_hugar

Reputation: 151

I faced the same issue with respect to opencv version 3.4.3.

With reference to this example, I figured out that I was not including the libopencv_videoio. Once I added it to the project, the build was successful.

In opencv version 3, I think we also need to include the library -lopencv_videoio to use VideoCapture.

Upvotes: 15

Lakshya Kejriwal
Lakshya Kejriwal

Reputation: 1388

The reason your code is not compiling is you are not giving the path of the libraries and the header files. Try compiling the code using the following command.

g++ main.cpp -o main -I <path to opencv header files> -L <path to opencv libraries> -l<name of libraries>

A sample example if you are using linux is 

g++ main.cpp -o main -I /usr/local/include -L /usr/local/lib -lopencv_core -lopencv_highgui

Here I am assuming your header file are in /usr/local/include and libraries are in /usr/local/lib and lopencv_core is the name of your library

Upvotes: 5

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