[英]“Undefined reference to” when using library in C++
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()' 当我在互联网上运行一些代码时遇到以下问题: http ://docs.opencv.org/doc/tutorials/objdetect/cascade_classifier/cascade_classifier.html:newmain.cpp :(。text + 0x17):未定义引用`cv :: VideoCapture :: VideoCapture()'
newmain.cpp:(.text+0x35): undefined reference to `cv::CascadeClassifier::load(std::string const&)' newmain.cpp :(。text + 0x35):对`cv :: CascadeClassifier :: load(std :: string const&)'的未定义引用
newmain.cpp:(.text+0x5f): undefined reference to `cv::CascadeClassifier::load(std::string const&)' newmain.cpp :(。text + 0x5f):对`cv :: CascadeClassifier :: load(std :: string const&)'的未定义引用
newmain.cpp:(.text+0x8e): undefined reference to `cv::VideoCapture::open(int)' newmain.cpp :(。text + 0x8e):对`cv :: VideoCapture :: open(int)'的未定义引用
newmain.cpp:(.text+0x9d): undefined reference to `cv::VideoCapture::isOpened() const' newmain.cpp :(。text + 0x9d):对`cv :: VideoCapture :: isOpened()const'的未定义引用
newmain.cpp:(.text+0x116): undefined reference to `cv::waitKey(int)' newmain.cpp :(。text + 0x116):对`cv :: waitKey(int)'的未定义引用
newmain.cpp:(.text+0x141): undefined reference to `cv::VideoCapture::read(cv::Mat&)' newmain.cpp :(。text + 0x141):对`cv :: VideoCapture :: read(cv :: Mat&)'的未定义引用
(the list goes on but all the same type of error) (列表继续但所有相同类型的错误)
The code is supposed to detect faces and eyes from pictures. 该代码应该从图片中检测面部和眼睛。
The code uses some functions from opencv2, which I have installed: 代码使用opencv2中的一些函数,我已经安装了这些函数:
#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 );
}
Thanks for any help you can give me! 感谢你给与我的帮助!
看来,你没有链接到任何opencv库。
gcc objDetection.cpp -o objDetection -lopencv_core -lopencv_imgproc -lopencv_objdetect -lopencv_highgui
As berak said, you need to link the these libraries. 正如berak所说,你需要链接这些库。 To do it at your project on eclipse, you should tell eclipse where find the Include files for opencv and Where are the libraries to link.
要在eclipse上的项目中执行此操作,您应该告诉eclipse在哪里找到opencv的Include文件以及要链接的库的位置 。
/usr/local/include/opencv
在/ usr /本地/包括/ OpenCV的
/usr/local/lib
在/ usr / local / lib目录
The original tutorial is at Opencv Documentation 最初的教程是在Opencv文档中
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