我正在使用OpenCV 3.2
我尝试使用FLANN以比暴力匹配更快地匹配特征描述符。
// Ratio to the second neighbor to consider a good match.
#define RATIO 0.75
void matchFeatures(const cv::Mat &query, const cv::Mat &target,
std::vector<cv::DMatch> &goodMatches) {
std::vector<std::vector<cv::DMatch>> matches;
cv::Ptr<cv::FlannBasedMatcher> matcher = cv::FlannBasedMatcher::create();
// Find 2 best matches for each descriptor to make later the second neighbor test.
matcher->knnMatch(query, target, matches, 2);
// Second neighbor ratio test.
for (unsigned int i = 0; i < matches.size(); ++i) {
if (matches[i][0].distance < matches[i][1].distance * RATIO)
goodMatches.push_back(matches[i][0]);
}
}
这段代码可以用SURF和SIFT描述符正常工作,但是不能用于ORB。
OpenCV Error: Unsupported format or combination of formats (type=0) in buildIndex
正如此处所说,FLANN需要描述符的类型为CV_32F,因此我们需要进行转换。
if (query.type() != CV_32F) query.convertTo(query, CV_32F);
if (target.type() != CV_32F) target.convertTo(target, CV_32F);
然而,这个所谓的修复方法在
convertTo
函数中又返回了另一个错误。OpenCV Error: Assertion failed (!fixedType() || ((Mat*)obj)->type() == mtype) in create
这个断言位于 opencv/modules/core/src/matrix.cpp
文件的第2277行。
发生了什么?
复现问题的代码。
#include <opencv2/opencv.hpp>
int main(int argc, char **argv) {
// Read both images.
cv::Mat image1 = cv::imread(argv[1], cv::IMREAD_GRAYSCALE);
if (image1.empty()) {
std::cerr << "Couldn't read image in " << argv[1] << std::endl;
return 1;
}
cv::Mat image2 = cv::imread(argv[2], cv::IMREAD_GRAYSCALE);
if (image2.empty()) {
std::cerr << "Couldn't read image in " << argv[2] << std::endl;
return 1;
}
// Detect the keyPoints and compute its descriptors using ORB Detector.
std::vector<cv::KeyPoint> keyPoints1, keyPoints2;
cv::Mat descriptors1, descriptors2;
cv::Ptr<cv::ORB> detector = cv::ORB::create();
detector->detectAndCompute(image1, cv::Mat(), keyPoints1, descriptors1);
detector->detectAndCompute(image2, cv::Mat(), keyPoints2, descriptors2);
// Match features.
std::vector<cv::DMatch> matches;
matchFeatures(descriptors1, descriptors2, matches);
// Draw matches.
cv::Mat image_matches;
cv::drawMatches(image1, keyPoints1, image2, keyPoints2, matches, image_matches);
cv::imshow("Matches", image_matches);
}
cv::FlannBasedMatcher matcher = cv::FlannBasedMatcher(cv::makePtr<cv::flann::LshIndexParams>(12, 20, 2));
。 - Santiago Gilif (matches[i].size() >= 2)
。 - Santiago GilFLANN_INDEX_LSH = 6
。 - scrutarimulti_probe_level
的注释,它是“在多探测中使用的级别数(标准LSH为0)”,因此最好使用multi_probe_level=0
。 - scrutari