[英]SURF Feature extraction and Keypoint match based on FlannBasedMatcher
以下是我的代碼,用於使用SURF提取特征,並使用flannBasedMatcher匹配點。
Mat object = imread("S6E0.bmp", CV_LOAD_IMAGE_GRAYSCALE);
if( !object.data )
{
// std::cout<< "Error reading object " << std::endl;
return -2;
}
//Detect the keypoints using SURF Detector
int minHessian = 500;
SurfFeatureDetector detector( minHessian );
std::vector<KeyPoint> kp_object;
detector.detect( object, kp_object );
//Calculate descriptors (feature vectors)
SurfDescriptorExtractor extractor;
Mat des_object;
extractor.compute( object, kp_object, des_object );
FlannBasedMatcher matcher;
char key = 'a';
//VideoCapture cap(0);
namedWindow("Good Matches");
std::vector<Point2f> obj_corners(4);
//Get the corners from the object
obj_corners[0] = cvPoint(0,0);
obj_corners[1] = cvPoint( object.cols, 0 );
obj_corners[2] = cvPoint( object.cols, object.rows );
obj_corners[3] = cvPoint( 0, object.rows );
Mat image = imread("S6E0.bmp", CV_LOAD_IMAGE_GRAYSCALE);
Mat des_image, img_matches;
std::vector<KeyPoint> kp_image;
std::vector<vector<DMatch >> matches;
std::vector<std::vector<cv::DMatch>> matches1;
std::vector<std::vector<cv::DMatch>> matches2;
std::vector<cv::DMatch> matches3;
std::vector<DMatch > good_matches;
std::vector<Point2f> obj;
std::vector<Point2f> scene;
std::vector<Point2f> scene_corners(4);
Mat H;
//cvtColor(frame, image, CV_RGB2GRAY);
detector.detect( image, kp_image );
extractor.compute( image, kp_image, des_image );
matcher.knnMatch(des_object, des_image, matches, 2);
for(int i = 0; i < min(des_image.rows-1,(int) matches.size()); i++) //THIS LOOP IS SENSITIVE TO SEGFAULTS
{
if((matches[i][0].distance < 0.6*(matches[i][1].distance)) && ((int) matches[i].size()<=2 && (int) matches[i].size()>0))
{
good_matches.push_back(matches[i][0]);
}
}
//Draw only "good" matches
drawMatches( object, kp_object, image, kp_image, good_matches, img_matches, Scalar::all(-1), Scalar::all(-1), vector<char>(), DrawMatchesFlags::NOT_DRAW_SINGLE_POINTS );
if (good_matches.size() >= 4)
{
printf("Images matching %d , %d", good_matches.size(), kp_object.size());
//return 1;
for( int i = 0; i < good_matches.size(); i++ )
{
//Get the keypoints from the good matches
obj.push_back( kp_object[ good_matches[i].queryIdx ].pt );
scene.push_back( kp_image[ good_matches[i].trainIdx ].pt );
}
//H = findHomography( obj, scene, CV_RANSAC );
//printf("Size : %d", H.size());
//perspectiveTransform( obj_corners, scene_corners, H);
//printf("Size : %d --- %d --- %d", H.size(), scene_corners.size());
}else{
printf("Images matching %d , %d", good_matches.size(), kp_object.size());
}
//Show detected matches
imshow( "Good Matches", img_matches );
waitKey(0);
return 0;
在這段代碼中,我想知道通過這種方法究竟發生了什么
matcher.knnMatch(des_object, des_image, matches, 2);
據我所知,我傳遞了匹配圖像的兩個描述符, 匹配向量用2個最近鄰居填充。 我想知道方法中究竟發生了什么,以及如何填充匹配方法以及填充哪些點。
在此代碼段中
for(int i = 0; i < min(des_image.rows-1,(int) matches.size()); i++) //THIS LOOP IS SENSITIVE TO SEGFAULTS
{
if((matches[i][0].distance < 0.6*(matches[i][1].distance)) && ((int) matches[i].size()<=2 && (int) matches[i].size()>0))
{
good_matches.push_back(matches[i][0]);
}
}
我使用最近的neibour距離比(nndr)為0.6,我想知道如何找出good_matches以及nndr值的變化將如何影響。
如果我可以解決這個代碼,那將是一個很大的幫助。 謝謝。
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