OpenCV 构建 G++ 符号 error/DSO 错误

Question

我正在研究基于 Rpi 的自动驾驶汽车 - 我利用 OpenCV 从 pi 相机进行图像处理，以遵循预先设计的轨道。我目前正在尝试让它工作（一个基本的视频流选项），以了解在我开发用于图像录制的 NN 之前如何让它工作。

我的代码如下（由于opencv错误拒绝构建）：

#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;
}

输出如下：

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

-l<library> 标志需要跟在使用它们的源或对象 (.o) 文件之后。

链接器是这样工作的：它从命令行从左到右处理 .cpp/.o 文件，并且不知道它需要从库中得到什么，直到它看到它们在 .cpp/.o 文件。

因此更改链接器命令：

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

我遇到了同样的问题，但是我用 pkg-config opencv --cflags --libs 解决了它。

当我用前面的命令编译时，输出如下：

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

虽然问题解决了，但我仍然想知道为什么。谁能解释一下？

OpenCV 构建 G++ 符号 error/DSO 错误

OpenCV build G++ symbol error/DSO error

c++

opencv

raspbian

opencv3.0

raspberry-pi3