编译时 SIFT 代码 (C++) 中的未定义引用

Question

我正在尝试检测关键点并提取一组图像的描述符并将它们存储在文本文件中以进行匹配（这将由另一段代码处理）。这是我目前所有的代码。

以下是我尝试在 Ubuntu 12.04 终端上使用 g++ sift1.cpp 编译的代码。我安装了 OpenCV 2.4.9。

#include <iostream>
#include <stdio.h>
#include <dirent.h>
#include <fstream>
#include <string>
#include <vector>
#include <iterator>
#include <opencv2/opencv.hpp>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/nonfree/features2d.hpp>
#include <opencv2/features2d/features2d.hpp>

using namespace std;
using namespace cv;

int main(int argc, char** argv)
{
    if(argc != 2)
    {
        cout << "Usage: ./output <database path>" << endl;
        return -1;
    }
    Mat img;
    vector<KeyPoint> keypoints;
    //  SiftFeatureDetector detector;
    //  vector<KeyPoint> keypoints;
    //      detector.detect(img, keypoints);
    Mat descriptor;
    SIFT sift;
    Mat frame_gray;
    //  vector<Rect> faces;
    ofstream outfile_kp, outfile_des;
    outfile_kp.open("keypoints_file.txt");
    outfile_des.open("descriptors_file.txt");
    DIR *pdir = NULL;
    pdir = opendir(argv[1]);
    struct dirent *pent = NULL;
    while(pent == readdir(pdir))
    {
        if((strcmp(pent -> d_name, ".") == 0) || (strcmp(pent -> d_name, "..") == 0))
        {
            continue;
        }
        img = imread(pent -> d_name, CV_LOAD_IMAGE_GRAYSCALE);
        cvtColor( img, frame_gray, CV_BGR2GRAY );
        equalizeHist( frame_gray, frame_gray );
        sift.operator()(frame_gray,frame_gray,keypoints,descriptor,false);
        //      std::ostream_iterator<KeyPoint> output_iterator_kp(outfile_kp, "\n");
        //      std::copy(keypoints.begin(), keypoints.end(), output_iterator_kp);
        //      outfile_des << descriptor << endl;
        //      std::ostream_iterator<KeyPoint> output_iterator_des(output_des, "\n");
        //      std::copy(keypoints.begin(), keypoints.end(), output_iterator_des);
        //      outfile_kp << keypoints << endl;
        //      outfile_des << descriptor << endl;
    }
    outfile_kp.close();
    outfile_des.close();
    /*
       Mat img_keypoints;      drawkeypoints(img,keypoints,img_keypoints,Scalar::all(-1),DrawMatchesFlags::DEFAULT);
       imshow("keypoints",img_keypoints);
     */
    waitKey(0);
    return 0;
}

下面是我得到的错误：

/tmp/ccqW6zsl.o: In function `main':
sift1.cpp:(.text+0xc1): undefined reference to `cv::SIFT::SIFT(int, int, double, double, double)'
sift1.cpp:(.text+0x20e): undefined reference to `cv::imread(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, int)'
sift1.cpp:(.text+0x26b): undefined reference to `cv::_OutputArray::_OutputArray(cv::Mat&)'
sift1.cpp:(.text+0x283): undefined reference to `cv::_InputArray::_InputArray(cv::Mat const&)'
sift1.cpp:(.text+0x2ab): undefined reference to `cv::cvtColor(cv::_InputArray const&, cv::_OutputArray const&, int, int)'
sift1.cpp:(.text+0x2c3): undefined reference to `cv::_OutputArray::_OutputArray(cv::Mat&)'
sift1.cpp:(.text+0x2db): undefined reference to `cv::_InputArray::_InputArray(cv::Mat const&)'
sift1.cpp:(.text+0x2f3): undefined reference to `cv::equalizeHist(cv::_InputArray const&, cv::_OutputArray const&)'
sift1.cpp:(.text+0x30b): undefined reference to `cv::_OutputArray::_OutputArray(cv::Mat&)'
sift1.cpp:(.text+0x323): undefined reference to `cv::_InputArray::_InputArray(cv::Mat const&)'
sift1.cpp:(.text+0x33b): undefined reference to `cv::_InputArray::_InputArray(cv::Mat const&)'
sift1.cpp:(.text+0x379): undefined reference to `cv::SIFT::operator()(cv::_InputArray const&, cv::_InputArray const&, std::vector<cv::KeyPoint, std::allocator<cv::KeyPoint> >&, cv::_OutputArray const&, bool) const'
sift1.cpp:(.text+0x3c3): undefined reference to `cv::waitKey(int)'
/tmp/ccqW6zsl.o: In function `cv::Mat::~Mat()':
sift1.cpp:(.text._ZN2cv3MatD2Ev[_ZN2cv3MatD5Ev]+0x2b): undefined reference to `cv::fastFree(void*)'
/tmp/ccqW6zsl.o: In function `cv::Mat::operator=(cv::Mat const&)':
sift1.cpp:(.text._ZN2cv3MataSERKS0_[cv::Mat::operator=(cv::Mat const&)]+0xf2): undefined reference to `cv::Mat::copySize(cv::Mat const&)'
/tmp/ccqW6zsl.o: In function `cv::Mat::release()':
sift1.cpp:(.text._ZN2cv3Mat7releaseEv[cv::Mat::release()]+0x3b): undefined reference to `cv::Mat::deallocate()'
/tmp/ccqW6zsl.o: In function `cv::Feature2D::~Feature2D()':
sift1.cpp:(.text._ZN2cv9Feature2DD2Ev[cv::Feature2D::~Feature2D()]+0x46): undefined reference to `cv::DescriptorExtractor::~DescriptorExtractor()'
sift1.cpp:(.text._ZN2cv9Feature2DD2Ev[cv::Feature2D::~Feature2D()]+0x5b): undefined reference to `cv::FeatureDetector::~FeatureDetector()'
sift1.cpp:(.text._ZN2cv9Feature2DD2Ev[cv::Feature2D::~Feature2D()]+0x72): undefined reference to `cv::Algorithm::~Algorithm()'
sift1.cpp:(.text._ZN2cv9Feature2DD2Ev[cv::Feature2D::~Feature2D()]+0xa2): undefined reference to `cv::FeatureDetector::~FeatureDetector()'
sift1.cpp:(.text._ZN2cv9Feature2DD2Ev[cv::Feature2D::~Feature2D()]+0xbd): undefined reference to `cv::Algorithm::~Algorithm()'
/tmp/ccqW6zsl.o: In function `cv::SIFT::~SIFT()':
sift1.cpp:(.text._ZN2cv4SIFTD1Ev[cv::SIFT::~SIFT()]+0x1e): undefined reference to `vtable for cv::SIFT'
sift1.cpp:(.text._ZN2cv4SIFTD1Ev[cv::SIFT::~SIFT()]+0x30): undefined reference to `vtable for cv::SIFT'
sift1.cpp:(.text._ZN2cv4SIFTD1Ev[cv::SIFT::~SIFT()]+0x37): undefined reference to `vtable for cv::SIFT'
sift1.cpp:(.text._ZN2cv4SIFTD1Ev[cv::SIFT::~SIFT()]+0x42): undefined reference to `VTT for cv::SIFT'
sift1.cpp:(.text._ZN2cv4SIFTD1Ev[cv::SIFT::~SIFT()]+0x6b): undefined reference to `cv::Algorithm::~Algorithm()'
sift1.cpp:(.text._ZN2cv4SIFTD1Ev[cv::SIFT::~SIFT()]+0x9d): undefined reference to `cv::Algorithm::~Algorithm()'
collect2: ld returned 1 exit status

我无法解决这些问题。任何见解将不胜感激。提前致谢。

Answer 1

您遇到的是 link编译代码时出现的错误。这是因为编译代码时，编译器找不到 OpenCV 库。因此，编译代码时需要 link 使用 OpenCV 库。

简单地说，这样做：

$ g++ -Wall -g -o sift sift.cpp `pkg-config --cflags --libs opencv`

g++ 的上述选项启用所有警告，启用调试模式并将输出可执行文件称为 sift。

在运行你的代码之后，做：

$ ./sift

编译时 SIFT 代码 (C++) 中的未定义引用

Undefined references in SIFT code (C++) while compiling

c++

opencv

image-processing

sift