FREAK descriptor extractor returns empty Mat
I have a detector (Dense) and when I extract the descriptors I get a Mat with 0 rows and 64 columns:
KeyPointVector keypoints;
m_detector->detect(image, keypoints);
cv::Mat descriptors;
m_extractor->compute(image, keypoints, descriptors); // keypoints is not empty
Am I doing something wrong? Or FREAK extractor does not work with the Dense?
I have also tried with other detectors, and the results are here:
FAST + FREAK => descriptors(cols = 64, rows = 0)
STAR + FREAK => descriptors(cols = 0, rows = 0)
ORB + FREAK => descriptors(cols = 0, rows = 0)
BRISK + FREAK => descriptors(cols = 0, rows = 0)
MSER + FREAK => descriptors(cols = 64, rows = 0)
GFTT + FREAK => descriptors(cols = 64, rows = 0)
HARRIS + FREAK => descriptors(cols = 64, rows = 0)
Dense + FREAK => descriptors(cols = 64, rows = 0)
SimpleBlob + FREAK => descriptors(cols = 64, rows = 0)
Could it be because of the image size? I am using images of cols = 144, rows = 33. Or should the image be colored?
did you try another one, like Fast ? (iirc gftt only returns valid points, but no octave, response or angle)
I've tried FAST, but it seems that it is the same... empty Mat. I use OpenCV 2.4.10 under Linux
BRIEF is also crashing with Dense and it seems that BRISK is working... Is there a bug? Shall I init something like initModule_nonfree for SIFT and SURF?
It seems that it is the size: I have resized the image and there have appeared descriptors (using Dense and FREAK) (double size -> 164 descriptors from 528 keypoints)
@berak Do you know something about the minimum size an image should be for having FREAK descriptors?
no, but that might be a reason. how small was it ?
I have edited the question 144x33