Undefined symbols for architecture x86_64 Using QT6 with Opencv in OSX mac

Question

I faced this problem using qt6 and OpenCv4 on mac osx. I Checked these link1, link2, link3, link4 but none of them solved the problem.

Here is log Error I got :

Undefined symbols for architecture x86_64:
      "cv::imread(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, int)", referenced from:
          _main in main.o
    ld: symbol(s) not found for architecture x86_64
    clang: error: linker command failed with exit code 1 (use -v to see invocation)
    make: *** [opencv_test_qmake.app/Contents/MacOS/opencv_test_qmake] Error 1
    15:19:36: The process "/usr/bin/make" exited with code 2.
    Error while building/deploying project opencv_test_qmake (kit: Desktop Qt 6.1.1 clang 64bit)
    When executing step "Make"

score 0 · Answer 1 · answered Jun 25 '21 at 12:15

This problem mainly occurs, when a library is not included.

When using qmake, your .pro file needs to be like this:

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

CONFIG += c++11

SOURCES += \
    main.cpp \
    dialog.cpp

HEADERS += \
    dialog.h

FORMS += \
    dialog.ui


#Added Lines for OpenCV
INCLUDEPATH += /usr/local/include/opencv4
LIBS += -L/usr/local/lib \
LIBS += -lopencv_core -lopencv_imgproc -lopencv_features2d -lopencv_highgui -lopencv_calib3d -lopencv_imgcodecs -lopencv_videoio
QMAKE_MACOSX_DEPLOYMENT_TARGET = 11.0

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

Notice that the library -lopencv_imgcodecs is required if you are using imread -and the library lopencv_videoio is required when using videoCapture.

THe following main.cpp can be used to check the setup using an image and imread:

#include "dialog.h"
#include <QApplication>

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Dialog w;

    cv::Mat image= cv::imread("/Users/apple/Desktop/dog.jpg");

    // create image window named "My Image"
    cv::namedWindow("My Image");
    // show the image on window
    cv::imshow("My Image", image);
    // wait key for 5000 ms
    cv::waitKey(5000);

    w.show();
    return a.exec();
}

this main.cpp file can be used to check Videocapture and setup:

#include "opencv2/core.hpp"
#include "opencv2/imgproc.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/videoio.hpp"
#include <iostream>

using namespace cv;
using namespace std;

void drawText(Mat & image);

int main()
{
    cout << "Built with OpenCV " << CV_VERSION << endl;
    Mat image;
    VideoCapture capture;
    capture.open(0);
    if(capture.isOpened())
    {
        cout << "Capture is opened" << endl;
        for(;;)
        {
            capture >> image;
            if(image.empty())
                break;
            drawText(image);
            imshow("Sample", image);
            if(waitKey(10) >= 0)
                break;
        }
    }
    else
    {
        cout << "No capture" << endl;
        image = Mat::zeros(480, 640, CV_8UC1);
        drawText(image);
        imshow("Sample", image);
        waitKey(0);
    }
    return 0;
}

void drawText(Mat & image)
{
    putText(image, "Hello OpenCV",
            Point(20, 50),
            FONT_HERSHEY_COMPLEX, 1, // font face and scale
            Scalar(255, 255, 255), // white
            1, LINE_AA); // line thickness and type
}

If using Cmake instead of qmake, you can use the same main.cpp files. The only thing you need to do is to add these lines to the bottom of CmakeList.txt where opencv_test_102 is the name of the project folder.

#1 Specify OpenCV folder, and take care of dependencies and includes
set(OpenCV_DIR /usr/local/include/opencv4)
find_package(OpenCV REQUIRED)
include_directories(${OpenCV_INCLUDE_DIRS})


#2 Specify OpenCV library
target_link_libraries(opencv_test_102 PRIVATE ${OpenCV_LIBS})

Undefined symbols for architecture x86_64 Using QT6 with Opencv in OSX mac

1 Answers1