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matlabopencvubuntu-14.04mexfeature-extraction

Extract BRIEF features with mexopencv

I am trying to extract binary features in Matlab with mexopencv. If I use ORB as a detector and extractor everything works fine. The problem is when I try to use BRIEF extractor. This is the code I am using:

detector = cv.FeatureDetector('ORB');
extractor = cv.DescriptorExtractor('BRIEF'); % if I use 'ORB' here everything works fine

img = read('my-image');
keyPoints = detector.detect(img);
descriptors = extractor.compute(img, keyPoints);

And I get the following error:

Warning: The following error was caught while executing 'cv.DescriptorExtractor' class destructor: MxArray is not a scalar

In extract_train_orb (line 5) Error using DescriptorExtractor_ Unrecognized extractor BRIEF

Error in cv.DescriptorExtractor (line 63) this.id = DescriptorExtractor_(0, 'new', extractorType, varargin{:});

Error in extract_train_orb (line 2) extractor = cv.DescriptorExtractor('BRIEF');

I do not know how to solve this issue, as the mexopencv's documentation says BRIEF is a supported extractor.

Anyone has any idea? Thanks

EDIT:

In fact, ORB is the only type currently working. 'BRIEF', 'SURF' and 'SIFT' types are getting the same error.

I am using OpenCV 3.0 and Matlab R2015b under Ubuntu 14.04.

EDIT 2:

contrib module was not installed. I download opencv_contrib, re-build & re-install OpenCV and finally, try to compile mexopencv contrib module by: 

make MATLABDIR=/usr/local/MATLAB/R2015b contrib

Compilation fails with this error:

/tmp/mex_619067277620954_21116/BriefDescriptorExtractor_.o: In function ``mexFunction': BriefDescriptorExtractor_.cpp:(.text+0x31d8): undefined reference to `createBriefDescriptorExtractor(__gnu_cxx::__normal_iterator > >, __gnu_cxx::__normal_iterator > >)' collect2: error: ld returned 1 exit status

Solution

  • I solved the problem thanks to @Miki suggestions.

    1. First, the contrib module should be installed. I re-installed OpenCV 3.0 as in this guide. Then, I run make clean, make and make contrib on mexopencv directory.

    2. Finally, I had to use

      extractor = cv.DescriptorExtractor('BriefDescriptorExtractor');

      instead of

      extractor = cv.DescriptorExtractor('BRIEF');