OpenCV 3: List of available FeatureDetector::create() and DescriptorExtractor::create() options?

Question

edit: I was looking at the wrong OpenCV2 code example, there is no FeatureDetector::create in OpenCV3 - this was confusing me.

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Hey new to OpenCV and learning by example by pulling apart other peoples C++ code.

I would like to try all available options for:

detector = FeatureDetector::create(str_detector);
descriptor = DescriptorExtractor::create(str_descriptor);

currently str_detector is FAST and str_descriptor is BRISK

I am having trouble finding what available Detectors and Descriptors are available to me.

Is there a way to output a list of all currently available options?

(I have just built the latest opencv + opencv-contrib from github on a fresh linux install)

I have found a list of 3rd party files here https://github.com/Itseez/opencv_contrib/tree/master/modules/xfeatures2d/src - I think these are 3rd Descriptors and Detectors because those words are mentioned in some of the files. However it would be nice to have a full list of currently compiled/available options to play with.

Thanks!

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Trying to find the answer myself, edits as I go:

1. Found typedef Feature2D FeatureDetector and typedef Feature2D DescriptorExtractor in modules/features2d/include/opencv2/features2d.hpp
2. Digging for Feature2D now...
3. I'm so confused, my C++ is failing me, there is no create in https://github.com/Itseez/opencv/blob/master/modules/features2d/src/feature2d.cpp
4. ok so just looking through the code ( https://github.com/Itseez/opencv/blob/master/modules/features2d/include/opencv2/features2d.hpp )
   • BRISK
   • ORB
   • MSER
   • FastFeatureDetector / FAST
   • AgastFeatureDetector / AGAST
   • GFTTDetector
   • SimpleBlobDetector
   • KAZE / AKAZE
5. and from the contrib code ( https://github.com/Itseez/opencv_contrib/blob/master/modules/xfeatures2d/include/opencv2/xfeatures2d.hpp )
   • FREAK
   • StarDetector
   • BriefDescriptorExtractor
   • LUCID
   • LATCH
   • DAISY
   • MSDDetector
6. and from nonfree contrib code ( https://github.com/Itseez/opencv_contrib/blob/master/modules/xfeatures2d/include/opencv2/xfeatures2d/nonfree.hpp )
   • SIFT
   • SURF
7. Still unsure which of the above can/should be used for FeatureDetector or DescriptorExtractor

Answer 1

You have also the OpenCV documentation to have a list of OpenCV features:

• OpenCV 3.1 documentation
• OpenCV 3.1 contrib documentation

What I do to know if the feature is available only in keypoints detection or descriptor extraction or both is to read the corresponding paper linked in the documentation. It allows also to have a brief description of the features (for example if it is a binary descriptor, main advantages, etc.)

Other solution is to test each feature:

• if the call to detect() is ok (no exception thrown) ==> feature detection
• if the call to compute() is ok ==> feature extraction
• if the call to detectAndCompute() is ok ==> both
• or looking directly into the source code.

Maybe a more optimal solution exists...

Anyway, from my knowledge (feel free to correct me if I am wrong):

• BRISK: detector + descriptor
• ORB: detector + descriptor
• MSER: detector
• FAST: detector
• AGAST: detector
• GFFT: detector
• SimpleBlobDetector: detector
• KAZE: detector + descriptor
• AKAZE: detector + descriptor
• FREAK: descriptor
• StarDetector: detector
• BriefDescriptorExtractor: descriptor
• LUCID: descriptor
• LATCH: descriptor
• DAISY: descriptor
• MSDDetector: detector
• SIFT: detector + descriptor
• SURF: detector + descriptor

Also with OpenCV 3.1, the code is:

cv::Ptr<cv::Feature2D> kaze = cv::KAZE::create(); 
std::vector<cv::KeyPoint> kpts; 
cv::Mat descriptors; 
kaze->detect(matImg, kpts); 
kaze->compute(matImg, kpts, descriptors); 
kaze->detectAndCompute(matImg, cv::noArray(), kpts, descriptors);

cv::Ptr<cv::Feature2D> daisy = cv::xfeatures2d::DAISY::create(); //Contrib

To know which norm type to use:

  std::cout << "AKAZE: " << akaze->descriptorType() << " ; CV_8U=" << CV_8U << std::endl;
  std::cout << "AKAZE: " << akaze->defaultNorm() << " ; NORM_HAMMING=" << cv::NORM_HAMMING << std::endl;

Finally, why

No more features2d::create?