I am using SURF for detecting specific objects. But the issue with my code is the rectangle is drawn even if the object is not present in the scene. Like if i remove the object from the scene the rectangle stays there. I have no issues with detection it works perfectly.
//Ptr<SIFT> detector = SIFT::create(0,5,0.03,18);
Ptr<SURF> detector = SURF::create(minHessian,4,2);
Ptr<DescriptorExtractor> extractor = SURF::create(minHessian,4,2);
//Ptr<DescriptorExtractor> extractor = SIFT::create(0,5,0.03,18);
cvtColor(dst, src, CV_BGR2GRAY);
cvtColor(frame, gray_image, CV_BGR2GRAY);
detector->detect(src, keypoints_1);
//printf("Object: %d keypoints detected\n", (int)keypoints_1.size());
detector->detect(gray_image, keypoints_2);
//printf("Object: %d keypoints detected\n", (int)keypoints_1.size());
extractor->compute(src, keypoints_1, img_extractor);
// printf("Object: %d descriptors extracted\n", img_extractor.rows);
extractor->compute(gray_image, keypoints_2, snap_extractor);
std::vector<Point2f> scene_corners(4);
std::vector<Point2f> obj_corners(4);
obj_corners[0] = (cvPoint(0, 0));
obj_corners[1] = (cvPoint(src.cols, 0));
obj_corners[2] = (cvPoint(src.cols, src.rows));
obj_corners[3] = (cvPoint(0, src.rows));
vector<DMatch> matches;
matcher.match(img_extractor, snap_extractor, matches);
double max_dist = 0; double min_dist = 100;
//-- Quick calculation of max and min distances between keypoints
for (int i = 0; i < img_extractor.rows; i++)
{
double dist = matches[i].distance;
if (dist < min_dist) min_dist = dist;
if (dist > max_dist) max_dist = dist;
}
printf("-- Max dist : %f \n", max_dist);
printf("-- Min dist : %f \n", min_dist);
vector< DMatch > good_matches;
for (int i = 0; i < img_extractor.rows; i++)
{
if (matches[i].distance <= max(2 * min_dist, 0.02))
{
good_matches.push_back(matches[i]);
}
}
Mat img_matches;
vector< DMatch > emptyVec;
drawMatches(src, keypoints_1, gray_image, keypoints_2, emptyVec,
img_matches, Scalar::all(-1), Scalar::all(-1),
vector<char>(), DrawMatchesFlags::NOT_DRAW_SINGLE_POINTS);
if (good_matches.size() >= 4){
for (size_t i = 0; i<good_matches.size(); i++){
//get the keypoints from good matches
obj.push_back(keypoints_1[good_matches[i].queryIdx].pt);
scene.push_back(keypoints_2[good_matches[i].trainIdx].pt);
}
}
H = findHomography(obj, scene, CV_RANSAC);
perspectiveTransform(obj_corners, scene_corners, H);
line(img_matches, scene_corners[0] + Point2f(src.cols, 0), scene_corners[1] + Point2f(src.cols, 0), Scalar(0, 255, 0), 4);
line(img_matches, scene_corners[1] + Point2f(src.cols, 0), scene_corners[2] + Point2f(src.cols, 0), Scalar(0, 255, 0), 4);
line(img_matches, scene_corners[2] + Point2f(src.cols, 0), scene_corners[3] + Point2f(src.cols, 0), Scalar(0, 255, 0), 4);
line(img_matches, scene_corners[3] + Point2f(src.cols, 0), scene_corners[0] + Point2f(src.cols, 0), Scalar(0, 255, 0), 4);
I want to draw rectangle only when the object in the scene is detected. How do i do it?
