OpenCV: Flann matcher crashes

opencv

Solution

Probably you have tried to use KD-Tree or KMeans? They works only for CV_32F descriptors like SIFT or SURF. For binary descriptors like BRIEF\ORB\FREAK you have to use either LSH or Hierarchical clustering index. Or simple bruteforce search. You can manage it automatically, for example like this.

cv::flann::Index GenFLANNIndex(cv::Mat keys)
{
  switch (keys.type())
    {
    case CV_32F:
      {
        return  cv::flann::Index(keys,cv::flann::KDTreeIndexParams(4));
        break;
       }
    case CV_8U:
      {
        return cv::flann::Index(keys,cv::flann::HierarchicalClusteringIndexParams(),dist_type);
        break;
      }
    default:
      {
        return cv::flann::Index(keys,cv::flann::KDTreeIndexParams(4));
        break;
      }
    }

}
...
cv::flann::Index tree = GenFLANNIndex(descriptors);

Problem

I am trying to run an application that detects features in an image, but when I run the code for `BRISK` features, `BRIEF` descriptors and `FlannBased` matcher, it crashes and saying: ``` OpenCV Error: Unsupported format or combination of formats (type=0 ) in buildIndex_, file /home/stefan/git_repos/opencv/modules/flann/src/miniflann.cpp, line 315 terminate called after throwing an instance of 'cv::Exception' what(): /home/stefan/git_repos/opencv/modules/flann/src/miniflann.cpp:315: error: (-210) type=0 in function buildIndex_ Aborted (core dumped) ``` Any ideas why?

Original source