OpenCV error in codes - c++

Question

I'm doing a project on opencv on image matching.
The lines
std::vector<cv::Keypoint> keypoints1;
std::vector<cv::Keypoint> keypoints2;
have the error: namespace "cv" has no member "Keypoint"
How do i solve this?
Another error is in the code
//Define feature detector
cv::FastFeatureDetector fastDet(80);
//Keypoint detection
fastDet.detect(image1, keypoints1);
fastDet.detect(image2, keypoints2);
where the error says:
object of abstract class type "cv::FastFeatureDetector" is not allowed:
function :cv::FastFeatureDetector::setThreshold" is a pure virtual function
function :cv::FastFeatureDetector::getThreshold" is a pure virtual function
function :cv::FastFeatureDetector::setNonmaxSuppression" is a pure virtual function
function :cv::FastFeatureDetector::getNonmaxSuppression" is a pure virtual function
function :cv::FastFeatureDetector::setType" is a pure virtual function
function :cv::FastFeatureDetector::getType" is a pure virtual function
Can someone please help?
Here is the whole code:
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2\features2d\features2d.hpp"
#include"opencv2\core.hpp"
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <vector>
using namespace cv;
using namespace std;
void main(int argc, const char** argv)
{
Mat image1 = imread("image1.jpg", CV_LOAD_IMAGE_UNCHANGED);
Mat image2 = imread("image2.jpg", CV_LOAD_IMAGE_UNCHANGED);
//Define keypoints vector
std::vector<cv::Keypoint> keypoints1;
std::vector<cv::Keypoint> keypoints2;
//Define feature detector
cv::FastFeatureDetector fastDet(80);
//Keypoint detection
fastDet.detect(image1, keypoints1);
fastDet.detect(image2, keypoints2);
//Define a square neighbourhood
const int nsize(11); //size of the neighbourhood
cv::Rect neighbourhood(0, 0, nsize, nsize); //11x11
cv::Mat patch1;
cv::Mat patch2;
//For all points in first image
//find the best match in second image
cv::Mat result;
std::vector<cv::DMatch> matches;
//for all keypoints in image 1
for (int i = 0; i < keypoints1.size(); i++)
{
//define image patch
neighbourhood.x = keypoints1[i].pt.x - nsize / 2;
neighbourhood.y = keypoints1[i].pt.y - nsize / 2;
//if neighbourhood of points outside image,
//then continue with next point
if (neighbourhood.x < 0 || neighbourhood.y < 0 || neighbourhood.x + nsize >= image1.cols || neighbourhood.y + nsize >= image1.rows)
continue;
//patch in image 1
patch1 = image1(neighbourhood);
//reset best correlation value;
cv::DMatch bestMatch;
//for all keypoints in image 2
for (int j = 0; j < keypoints2.size(); j++)
{
//define image patch
neighbourhood.x = keypoints2[j].pt.x - nsize / 2;
neighbourhood.y = keypoints2[j].pt.y - nsize / 2;
//if neighbourhood of points outside image,
//then continue with next point
if (neighbourhood.x < 0 || neighbourhood.y < 0 || neighbourhood.x + nsize >= image2.cols || neighbourhood.y + nsize >= image2.rows)
continue;
//patch in image 2
patch2 = image2(neighbourhood);
//match the 2 patches
cv::matchTemplate(patch1, patch2, result, CV_TM_SQDIFF_NORMED);
//check if it is best match
if (result.at<float>(0, 0) < bestMatch.distance)
{
bestMatch.distance = result.at<float>(0, 0);
bestMatch.queryIdx = i;
bestMatch.trainIdx = j;
}
}
//add the best match
matches.push_back(bestMatch);
}
//extract the 25 best matches
std::nth_element(matches.begin(), matches.begin() + 25, matches.end());
matches.erase(matches.begin() + 25, matches.end());
//Draw matching results
cv::Mat matchImage;
cv::DrawMatchesFlags();
}

Answer 1

There are some mistakes in your code.
Replace belowe line
std::vector<cv::Keypoint> keypoints1;
std::vector<cv::Keypoint> keypoints2;
with this
std::vector<cv::KeyPoint> keypoints1;
std::vector<cv::KeyPoint> keypoints2;
For cv::FastFeatureDetector fastDet(80); may be you need to include library opencv_features2d
After this changes your code will run successfully.