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 chec

Answer 1

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&, cv::Rect_<int> const&)'

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'

...

Answer 2

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"

Answer 3

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.

Answer 4

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 <stdio.h>

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", &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

Answer 5

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)

Answer 6

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