c++ - BFMatcher knnMatch

Question

我尝试在 BFMatcher 上实现 knnMatch，如下所示:

BFMatcher matcher(NORM_L2, true);
vector<DMatch> matches;
//matcher.match(descriptors1, descriptors2, matches);
matcher.knnMatch(descriptors1, descriptors2, matches, 2);

并收到以下错误:

fiducialMain.cpp: In function ‘void fiducialCalc(cv::Mat, cv::Mat, cv::Mat&, cv::Mat&, int&)’:
fiducialMain.cpp:98:56: error: no matching function for call to ‘cv::BFMatcher::knnMatch(cv::Mat&, cv::Mat&, std::vector<cv::DMatch>&, int)’
  matcher.knnMatch(descriptors1, descriptors2, matches,2);
                                                        ^
fiducialMain.cpp:98:56: note: candidates are:
In file included from fiducialMain.cpp:15:0:
/usr/local/include/opencv2/features2d/features2d.hpp:1116:18: note: void cv::DescriptorMatcher::knnMatch(const cv::Mat&, const cv::Mat&, std::vector<std::vector<cv::DMatch> >&, int, const cv::Mat&, bool) const
     CV_WRAP void knnMatch( const Mat& queryDescriptors, const Mat& trainDescriptors,
                  ^
/usr/local/include/opencv2/features2d/features2d.hpp:1116:18: note:   no known conversion for argument 3 from ‘std::vector<cv::DMatch>’ to ‘std::vector<std::vector<cv::DMatch> >&’
/usr/local/include/opencv2/features2d/features2d.hpp:1130:18: note: void cv::DescriptorMatcher::knnMatch(const cv::Mat&, std::vector<std::vector<cv::DMatch> >&, int, const std::vector<cv::Mat>&, bool)
     CV_WRAP void knnMatch( const Mat& queryDescriptors, CV_OUT vector<vector<DMatch> >& matches, int k,
                  ^
/usr/local/include/opencv2/features2d/features2d.hpp:1130:18: note:   no known conversion for argument 2 from ‘cv::Mat’ to ‘std::vector<std::vector<cv::DMatch> >&’

谁能解释这个错误？

Answer 1

请再看看the docs

而普通的匹配函数有一个vector<DMatch>结果，

knnMatch(大声说:k-nearest-neighbours!)产生几个(k)个 vector ，因此你需要一个:

vector < vector >匹配

结果