I am trying to detect the keypoints and extract the descriptors of a set of images and store them in a text file for matching (which will be handled by another piece of code). This is all the code I have at the moment.
The following is the code that I'm trying to compile by using g++ sift1.cpp on the Ubuntu 12.04 terminal. I have OpenCV 2.4.9 installed.
#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;
}
And the following are the errors I get:
/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
I am unable to solve these issues. Any insight would be greatly appreciated. Thanks in advance.
What you are experiencing are linker errors when compiling your code. This is because when compiling your code, the compiler can't find the OpenCV libraries. Therefore, you need to link with the OpenCV libraries when compiling your code.
Simply put, do this:
$ g++ -Wall -g -o sift sift.cpp `pkg-config --cflags --libs opencv`
The above options for g++ enable all warnings, enable debug mode and will make the output executable called sift.
To run your code after, do:
$ ./sift