OpenCV 3.0 undefined reference error? - c++

Question

I've just followed the instructions to install opencv 3 on my ubuntu computer (I've already installed and ran programs using opencv 3 on a different linux device), however, when I tried to run one of my test programs from my old computer I get the following errors:
CMakeFiles/VideoTest.dir/VideoTest.cpp.o: In function `main':
VideoTest.cpp:(.text+0x6f): undefined reference to `cv::VideoWriter::fourcc(char,char,char, char)'
VideoTest.cpp:(.text+0xc3): undefined reference to `cv::VideoWriter::open(cv::String const&, int, double, cv::Size_<int>, bool)'
VideoTest.cpp:(.text+0x103): undefined reference to `cv::namedWindow(cv::String const&, int)'
VideoTest.cpp:(.text+0x146): undefined reference to `cv::VideoCapture::read(cv::_OutputArray const&)'
VideoTest.cpp:(.text+0x1b1): undefined reference to `cv::imshow(cv::String const&, cv::_InputArray const&)'
CMakeFiles/VideoTest.dir/VideoTest.cpp.o: In function `cv::String::String(char const*)':
VideoTest.cpp:(.text._ZN2cv6StringC2EPKc[_ZN2cv6StringC5EPKc]+0x3b): undefined reference to `cv::String::allocate(unsigned int)'
CMakeFiles/VideoTest.dir/VideoTest.cpp.o: In function `cv::String::~String()':
VideoTest.cpp:(.text._ZN2cv6StringD2Ev[_ZN2cv6StringD5Ev]+0xd): undefined reference to `cv::String::deallocate()'
collect2: ld returned 1 exit status
make[2]: *** [VideoTest] Error 1
make[1]: *** [CMakeFiles/VideoTest.dir/all] Error 2
make: *** [all] Error 2
Any idea what's going on? I'm relatively new to opencv. Here's my test code for reference:
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/opencv.hpp"
#include <iostream>
using namespace cv;
using namespace std;
int main(int argc, char* argv[]){
VideoCapture vCap(0);
VideoWriter vWrite;
vWrite.open("test.avi", vWrite.fourcc('M','J','P','G'), 20, Size(640, 480), true);
while (1) {
namedWindow("VideoFeed", WINDOW_AUTOSIZE);
Mat frame;
vCap.read(frame);
vWrite.write(frame);
imshow("VideoFeed", frame);
char c = waitKey(50);
if (c == 27) {
break;
}
}
return 0;
}
Thanks in advance.
Edit: My CMakeLists.txt:
cmake_minimum_required(VERSION 2.8)
project(VideoTest)
find_package(OpenCV REQUIRED)
add_executable(VideoTest VideoTest.cpp)
target_link_libraries(VideoTest ${OpenCV_LIBS})

Answer 1

VideoCapture and VideoWriter were moved to the videoio module in 3.0, so you have to additionally
#include "opencv2/videoio.hpp"
also, you don't seem to link to any of the required opencv libs, those are:
opencv_core, opencv_videoio, opencv_highgui

Answer 2

Alright, I've finally figured out what's going on. Something internally in the CMakeFiles folder went screwy when I moved the directory over to my new system. Removing all files/directories besides the project .cpp file and the CMakeLists.txt file, and running "cmake ." and "make" again seems to solve the problem.

Answer 3

Below cmake file works for me.
cmake_minimum_required(VERSION 3.5)
project(ImageProcessing)
set(CMAKE_CXX_STANDARD 14)
find_package(OpenCV REQUIRED)
include_directories( ${OpenCV_INCLUDE_DIRS} )
set(SOURCE_FILES main.cpp)
add_executable(ImageProcessing ${SOURCE_FILES})
target_link_libraries( ImageProcessing ${OpenCV_LIBS} )
# Print some message showing some of them
message(STATUS "OpenCV library status:")
message(STATUS " version: ${OpenCV_VERSION}")
message(STATUS " libraries: ${OpenCV_LIBS}")
message(STATUS " include path: ${OpenCV_INCLUDE_DIRS}")