“未定义的对...的引用”当在C ++中使用库 [英] "Undefined reference to" when using library in C++

问题描述

和我有以下问题时运行一些代码，我在互联网上找到从 http://docs.opencv.org/doc/tutorials/objdetect/cascade_classifier/cascade_classifier.html ：
newmain.cpp :(。text + 0x17）：未定义引用`cv： ：VideoCapture :: VideoCapture（）'

and i was having the following problem when running some code i found on the internet from http://docs.opencv.org/doc/tutorials/objdetect/cascade_classifier/cascade_classifier.html: newmain.cpp:(.text+0x17): undefined reference to `cv::VideoCapture::VideoCapture()'

newmain.cpp :(。text + 0x35）：未定义引用`cv :: CascadeClassifier :: load（std :: string const&）'

newmain.cpp:(.text+0x35): undefined reference to `cv::CascadeClassifier::load(std::string const&)'

newmain.cpp :(。text + 0x5f）：未定义引用`cv :: CascadeClassifier :: load（std :: string const&

newmain.cpp:(.text+0x5f): undefined reference to `cv::CascadeClassifier::load(std::string const&)'

newmain.cpp :(。text + 0x8e）：未定义引用`cv :: VideoCapture :: open（int）'

newmain.cpp:(.text+0x8e): undefined reference to `cv::VideoCapture::open(int)'

newmain.cpp :(。text + 0x9d）：未定义引用`cv :: VideoCapture :: isOpened（）const'

newmain.cpp:(.text+0x9d): undefined reference to `cv::VideoCapture::isOpened() const'

newmain.cpp （。text + 0x116）：未定义引用`cv :: waitKey（int）'

newmain.cpp:(.text+0x116): undefined reference to `cv::waitKey(int)'

newmain.cpp :(。 cv :: VideoCapture :: read（cv :: Mat&）'

newmain.cpp:(.text+0x141): undefined reference to `cv::VideoCapture::read(cv::Mat&)'

（列表继续，但所有相同类型的错误）

(the list goes on but all the same type of error)

代码应该从图片中检测脸部和眼睛。

The code is supposed to detect faces and eyes from pictures.

代码使用了opencv2中的一些函数， p>

The code uses some functions from opencv2, which I have installed:

    #include "opencv2/objdetect/objdetect.hpp"
    #include "opencv2/highgui/highgui.hpp"
    #include "opencv2/imgproc/imgproc.hpp"

    #include <iostream>
    #include <stdio.h>

    using namespace std;
    using namespace cv;

    /** Function Headers */
    void detectAndDisplay( Mat frame );

    /** Global variables */
    String face_cascade_name = "haarcascade_frontalface_alt.xml";
    String eyes_cascade_name = "haarcascade_eye_tree_eyeglasses.xml";
    CascadeClassifier face_cascade;
    CascadeClassifier eyes_cascade;
    String window_name = "Capture - Face detection";

    /** @function main */
    int main( void )
    {
        VideoCapture capture;
        Mat frame;

        //-- 1. Load the cascades
        if( !face_cascade.load( face_cascade_name ) ){ printf("--(!)Error loading face cascade\n"); return -1; };
        if( !eyes_cascade.load( eyes_cascade_name ) ){ printf("--(!)Error loading eyes cascade\n"); return -1; };

        //-- 2. Read the video stream
        capture.open( -1 );
        if ( ! capture.isOpened() ) { printf("--(!)Error opening video capture\n"); return -1; }

        while ( capture.read(frame) )
        {
            if( frame.empty() )
            {
                printf(" --(!) No captured frame -- Break!");
                break;
            }

            //-- 3. Apply the classifier to the frame
            detectAndDisplay( frame );

            int c = waitKey(10);
            if( (char)c == 27 ) { break; } // escape
        }
        return 0;
    }

    /** @function detectAndDisplay */
    void detectAndDisplay( Mat frame )
    {
        std::vector<Rect> faces;
        Mat frame_gray;

        cvtColor( frame, frame_gray, COLOR_BGR2GRAY );
        equalizeHist( frame_gray, frame_gray );

        //-- Detect faces
        face_cascade.detectMultiScale( frame_gray, faces, 1.1, 2, 0|CASCADE_SCALE_IMAGE, Size(30, 30) );

        for ( size_t i = 0; i < faces.size(); i++ )
        {
            Point center( faces[i].x + faces[i].width/2, faces[i].y + faces[i].height/2 );
            ellipse( frame, center, Size( faces[i].width/2, faces[i].height/2 ), 0, 0, 360, Scalar( 255, 0, 255 ), 4, 8, 0 );

            Mat faceROI = frame_gray( faces[i] );
            std::vector<Rect> eyes;

            //-- In each face, detect eyes
            eyes_cascade.detectMultiScale( faceROI, eyes, 1.1, 2, 0 |CASCADE_SCALE_IMAGE, Size(30, 30) );

            for ( size_t j = 0; j < eyes.size(); j++ )
            {
                Point eye_center( faces[i].x + eyes[j].x + eyes[j].width/2, faces[i].y + eyes[j].y + eyes[j].height/2 );
                int radius = cvRound( (eyes[j].width + eyes[j].height)*0.25 );
                circle( frame, eye_center, radius, Scalar( 255, 0, 0 ), 4, 8, 0 );
            }
        }
        //-- Show what you got
        imshow( window_name, frame );
    }

感谢任何帮助，您可以给我！

Thanks for any help you can give me!

推荐答案

似乎没有链接到任何opencv库。

it seems, you're not linking to any of the opencv libs.

gcc objDetection.cpp -o objDetection -lopencv_core -lopencv_imgproc -lopencv_objdetect -lopencv_highgui

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