Cannot get OpenCV to compile because of undefined references

Question

The code is simple and is essentially straight from this tutorial  I am running Arch Linux and have the OpenCV library stored at  usr include   I have also checked to ensure that  usr include is in my PATH     include  lt opencv cv h gt   include  lt opencv highgui h gt   include  lt iostream gt   using namespace cv    int main int argc  char   argv       Mat image      Mat grayImage        if  argv 1            std  cerr  lt  lt   No image data    lt  lt  std  endl          return -1              image   imread argv 1   1       cvtColor image  grayImage  CV BGR2GRAY       imwrite  Gray Image jpg   grayImage        namedWindow argv 1   CV WINDOW AUTOSIZE       namedWindow  Gray Image   CV WINDOW AUTOSIZE        imshow argv 1   image       imshow  Gray Image   grayImage        waitKey 0       return 0      The compiler process successfully finds and include these header files  but I still get undefined reference errors at compile-time  If you look into the header files I included they further include other files in  usr include opencv2  I have checked and such header files do exist    Any ideas     tmp ccudBcqD o  In function  main   test cpp   text 0xc0   undefined reference to  cv  imread std  string const amp   int   test cpp   text 0x11f   undefined reference to  cv   OutputArray   OutputArray cv  Mat amp    test cpp   text 0x138   undefined reference to  cv   InputArray   InputArray cv  Mat const amp    test cpp   text 0x158   undefined reference to  cv  cvtColor cv   InputArray const amp   cv   OutputArray const amp   int  int   test cpp   text 0x180   undefined reference to  cv   InputArray   InputArray cv  Mat const amp    test cpp   text 0x1ca   undefined reference to  cv  imwrite std  string const amp   cv   InputArray const amp   std  vector lt int  std  allocator lt int gt   gt  const amp    test cpp   text 0x241   undefined reference to  cv  namedWindow std  string const amp   int   test cpp   text 0x291   undefined reference to  cv  namedWindow std  string const amp   int   test cpp   text 0x2bf   undefined reference to  cv   InputArray   InputArray cv  Mat const amp    test cpp   text 0x2ff   undefined reference to  cv  imshow std  string const amp   cv   InputArray const amp    test cpp   text 0x32d   undefined reference to  cv   InputArray   InputArray cv  Mat const amp    test cpp   text 0x361   undefined reference to  cv  imshow std  string const amp   cv   InputArray const amp    test cpp   text 0x383   undefined reference to  cv  waitKey int    tmp ccudBcqD o  In function  cv  Mat   Mat     test cpp   text  ZN2cv3MatD2Ev  ZN2cv3MatD5Ev  0x39   undefined reference to  cv  fastFree void     tmp ccudBcqD o  In function  cv  Mat  operator  cv  Mat const amp     test cpp   text  ZN2cv3MataSERKS0   ZN2cv3MataSERKS0   0x111   undefined reference to  cv  Mat  copySize cv  Mat const amp     tmp ccudBcqD o  In function  cv  Mat  release     test cpp   text  ZN2cv3Mat7releaseEv  ZN2cv3Mat7releaseEv  0x47   undefined reference to  cv  Mat  deallocate    collect2  error  ld returned 1 exit status  Finished in 1 1s with exit code 1   shell cmd  g     home branden Desktop OpenCV test cpp  -o   home branden Desktop OpenCV test    dir   home branden Desktop OpenCV   path   usr local sbin  usr local bin  usr bin  usr bin vendor perl  usr bin core perl

User · Accepted Answer

This is a linker issue  Try   g   -o test 1 test 1 cpp  pkg-config opencv --cflags --libs    This should work to compile the source  However  if you recently compiled OpenCV from source  you will meet linking issue in run-time  the library will not be found   In most cases  after compiling libraries from source  you need to do finally   sudo ldconfig

User · Answer

If you do the following  you will be able to use opencv build from OpenCV INSTALL PATH   cmake minimum required VERSION 2 8   SET OpenCV INSTALL PATH  home user opencv opencv-2 4 13 release    SET OpenCV INCLUDE DIRS    OpenCV INSTALL PATH  include opencv   OpenCV INSTALL PATH  include    SET OpenCV LIB DIR    OpenCV INSTALL PATH  lib    LINK DIRECTORIES   OpenCV LIB DIR    set OpenCV LIBS opencv core opencv imgproc opencv calib3d opencv video opencv features2d opencv ml opencv highgui opencv objdetect opencv contrib opencv legacy opencv gpu     find package  OpenCV    project edge cpp   add executable edge edge cpp

User · Answer

if anyone still having this problem  One solution is to rebuild the source OpenCV library using MinGW and not use the binaries given by OpenCV  I did it and it worked like a charm

User · Answer

I have tried all solution  The -lopencv core -lopencv imgproc -lopencv highgui in comments solved my problem  And know my command line looks like this in geany   g   -lopencv core -lopencv imgproc -lopencv highgui  -o   e    f    When I build   g   -lopencv core -lopencv imgproc -lopencv highgui  -o  opencv   opencv cpp   in directory   home fedora Desktop Implementations    The headers are    include  opencv2 imgproc imgproc hpp   include  opencv2 highgui highgui hpp

User · Answer

For me  this type of error   mingw-w64-x86 64 lib gcc x86 64-w64-mingw32 8 2 0             x86 64-w64-mingw32 bin ld  mingw-w64-x86 64 x86 64-w64-mingw32 lib libTransform360 a VideoFrameTransform cpp obj  VideoFrameTransform cpp   text 0xc7c   undefined reference to  cv  Mat  Mat cv  Mat const amp   cv  Rect  lt int gt  const amp      meant load order  I had to do -lTransform360 -lopencv dnn345 -lopencv    just like that  that order  And putting them right next to each other helped too  don t put -lTransform360 all the way at the beginning   or you ll get  for some freaky reason   undefined reference to  VideoFrameTransform new  undefined reference to  VideoFrameTransform generateMapForPlane

User · Answer

follow this tutorial  i ran the install-opencv sh file in bash  its in the tutorial  read the example from openCV  CMakeLists txt  cmake minimum required VERSION 3 7  project openCVTest    cmake needs this line cmake minimum required VERSION 2 8     Define project name project opencv example project     Find OpenCV  you may need to set OpenCV DIR variable   to the absolute path to the directory containing OpenCVConfig cmake file   via the command line or GUI find package OpenCV REQUIRED     If the package has been found  several variables will   be set  you can find the full list with descriptions   in the OpenCVConfig cmake file    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     if CMAKE VERSION VERSION LESS  2 8 11         Add OpenCV headers location to your include paths     include directories   OpenCV INCLUDE DIRS   endif      Declare the executable target built from your sources add executable main main cpp     Link your application with OpenCV libraries target link libraries main   OpenCV LIBS     main cpp          file LinearBlend cpp     brief Simple linear blender   dst   alpha src1   beta src2       author OpenCV team       include  opencv2 imgcodecs hpp   include  opencv2 highgui hpp   include  lt stdio h gt   using namespace cv       Global Variables    const int alpha slider max   100  int alpha slider  double alpha  double beta       Matrices to store images    Mat src1  Mat src2  Mat dst       on trackbar          function on trackbar     brief Callback for trackbar     static void on trackbar  int  void          alpha    double  alpha slider alpha slider max        beta     1 0 - alpha         addWeighted  src1  alpha  src2  beta  0 0  dst        imshow   Linear Blend   dst          on trackbar           function main     brief Main function     int main  void             load          Read images   both have to be of the same size and type       src1   imread     data LinuxLogo jpg        src2   imread     data WindowsLogo jpg            load       if  src1 empty       printf  Error loading src1  n    return -1        if  src2 empty       printf  Error loading src2  n    return -1             Initialize values     alpha slider   0           window      namedWindow  Linear Blend   WINDOW AUTOSIZE      Create Window         window           create trackbar      char TrackbarName 50       sprintf  TrackbarName   Alpha x  d   alpha slider max        createTrackbar  TrackbarName   Linear Blend    amp alpha slider  alpha slider max  on trackbar            create trackbar           Show some stuff     on trackbar  alpha slider  0             Wait until user press some key     waitKey 0       return 0      Tested in linux mint 17

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