OpenCV build G ++符號錯誤/ DSO錯誤

Question

我正在研究基於Rpi的自駕車 - 我利用OpenCV從pi攝像頭進行圖像處理，以遵循預先設計的軌道。我目前正試圖讓這個工作（一個基本的視頻流選項），看看如何讓它開始工作，然後我開發到圖像記錄的NN。

我的代碼如下所示（它拒絕建立由於OpenCV的錯誤）：

#include <stdio.h> 
#include <pigpio.h> 
#include <stdlib.h> 
#include <unistd.h> 
#include <wiringPi.h> 
#include <softPwm.h> 
#include "move.h" 
#include "distance.h" 
#include <linux/videodev2.h> 
#include <libv4l2.h> 
#include <opencv2/core/core.hpp> 
#include <opencv2/opencv.hpp> 
#include <opencv2/imgcodecs.hpp> 
#include <opencv2/imgproc/imgproc.hpp> 
#include <opencv2/highgui/highgui.hpp> 
#include <opencv2/videoio.hpp> 
using namespace cv; 

void SysMenu(){ 
    system("clear"); 
int choice; 
    printf("||Please Choose An Option..........||\n"); 
    printf("||1.Test Motors || 2.Test Sensors||\n"); 
    printf("||3.Exit   ||    ||\n"); 
    scanf("%i",&choice); 

    switch(choice) 
{ 
case 1: 
    move(MT_FORWARD, 3000); 
    printf("fwd\n"); 
    move(MT_BACKWARD, 3000); 
    printf("bwd\n"); 
    move(MT_RIGHT, 3000); 
    printf("rght\n"); 
    move(MT_LEFT, 3000); 
    printf("left\n"); 
    move(MT_FORWARD | MT_RIGHT, 3000); 
    printf("fwd, right\n"); 
    move(MT_FORWARD | MT_LEFT, 3000); 
    printf("fwd left\n"); 
    delay(3000); 
    SysMenu(); 
    break; 

case 2 : 
    TestSensors(); 
    delay(3000); 
    SysMenu(); 
    break; 

case 3 : 
    break; 



default : printf("Input, Option Not available, Please retry"); 
    SysMenu(); 
    break; 
} 
} 

int main(int, char**) { 
VideoCapture cap; 
cap.cv::VideoCapture::open(0); 

if (!cap.isOpened()) 
return -1; 
Mat edge;//,gray,c_edge,lpf_gaussian_blurr; 
namedWindow("Original_Video",1); 


for(;;) 
{ 
    Mat video; 
    cap >> video;//capture live feed 

//convert to b&w 
cvtColor(video,edge,CV_BGR2GRAY); 




//Canny(gray,c_edge,0,30,3); 
//GaussianBlur(video,lpf_gaussian_blurr,Size(9,9),1.5,1.5); 

imshow("Original_Video",edge); 

if(waitKey(30)>= 0) break; 
} 


    initialisePins(); 
    SysMenu(); 
    gpioTerminate(); 

    return 0; 
} 

，輸出如下：

g++ -Wall -I/usr/local/include -lopencv_core -lwiringPi -lpigpio -lopencv_imgcodecs -lopencv_highgui -lopencv_videoio -lopencv_imgproc -o "SdCar" "SdCar.cpp" (in directory: /home/pi/selfdrivingcar-17) 
/usr/bin/ld: warning: libopencv_imgproc.so.3.1, needed by //usr/local/lib/libopencv_imgcodecs.so, may conflict with libopencv_imgproc.so.2.4 
/usr/bin/ld: warning: libopencv_core.so.3.1, needed by //usr/local/lib/libopencv_imgcodecs.so, may conflict with libopencv_core.so.2.4 
/usr/bin/ld: //usr/local/lib/libopencv_imgcodecs.so: undefined reference to symbol '_ZN2cv6String10deallocateEv' 
//usr/local/lib/libopencv_core.so.3.1: error adding symbols: DSO missing from command line 
Compilation failed. 
collect2: error: ld returned 1 exit status 

Answer 1

的-l<library>標誌需要按照源或對象（.o）使用它們的文件。

這是鏈接器是如何工作的：它處理命令行的.cpp/.o文件左到右，不知道它從庫需要，直到看到他們在.cpp/.o文件引用。

因此改變連接器的命令：

g++ -Wall -I/usr/local/include -lopencv_core -lwiringPi -lpigpio -lopencv_imgcodecs -lopencv_highgui -lopencv_videoio -lopencv_imgproc -o "SdCar" "SdCar.cpp" 

到

g++ -Wall -I/usr/local/include -o "SdCar" "SdCar.cpp" -lopencv_core -lwiringPi -lpigpio -lopencv_imgcodecs -lopencv_highgui -lopencv_videoio -lopencv_imgproc 

Answer 2

我遇到同樣的問題，但是我用pkg-config opencv --cflags --libs解決它。

當我和前面的命令編譯，輸出就像下面：

qsp@ubuntu:~/Documents/caffeProject/assign3$ g++ -o "test_mnist" 
"test_mnist.cpp" -lopencv_dnn -lopencv_highgui -lopencv_imgcodecs 
-lopencv_imgproc -lstdc++ -lopencv_core /usr/bin/ld: warning: libopencv_core.so.3.1, needed by //usr/local/lib/libopencv_dnn.so, may 
conflict with libopencv_core.so.2.4 /usr/bin/ld: /tmp/ccovch2b.o: 
    undefined reference to symbol '_ZN2cv6String10deallocateEv' 
    //usr/local/lib/libopencv_core.so.3.1: error adding symbols: DSO 
    missing from command line collect2: error: ld returned 1 exit status 

雖然問題解決了，我仍然不知道爲什麼。有人可以解釋嗎？