[OpenCV] Simple example C++ and ubuntu

Prerequisite:

Opencv is already installed.

Source code:

//include high gui headers

#include "opencv2/highgui/highgui.hpp"

//we are using standard and OpenCV namespaces

using namespace cv;

using namespace std;

int main( int argc, const char** argv ){

//create a window named theWindow

namedWindow("theWindow", CV_WINDOW_AUTOSIZE);

//wait user hit some key

waitKey(0);

//destroy window named theWindow

destroyWindow("theWindow");

return 0;

}

Build command:

g++ -o firstcv $(pkg-config --libs --cflags opencv) main.cpp

if error happened.

/tmp/cceyijPd.o: In function `main':

main.cpp:(.text+0x3d): undefined reference to `cv::namedWindow(cv::String const&, int)'

main.cpp:(.text+0x53): undefined reference to `cv::waitKey(int)'

main.cpp:(.text+0x70): undefined reference to `cv::destroyWindow(cv::String const&)'

/tmp/cceyijPd.o: In function `cv::String::String(char const*)':

main.cpp:(.text._ZN2cv6StringC2EPKc[_ZN2cv6StringC5EPKc]+0x4d): undefined reference to `cv::String::allocate(unsigned long)'

/tmp/cceyijPd.o: In function `cv::String::~String()':

main.cpp:(.text._ZN2cv6StringD2Ev[_ZN2cv6StringD5Ev]+0x14): undefined reference to `cv::String::deallocate()'

collect2: error: ld returned 1 exit status

It came from a linker, please try :

g++ -o main main.cpp `pkg-config opencv --cflags --libs`

Reference:

https://linoxide.com/linux-how-to/computer-vision-development-opencv-ubuntu/

https://stackoverflow.com/questions/24337932/cannot-get-opencv-to-compile-because-of-undefined-references