2 comments

1. Alexej

   %A, 21UTCThu, 21 Jul 2011 19:31:51 +0000 %e. %B %Y um %H:%M

   Thank you for your wonderful articles and in particular for your simple demo sources. This helped me a lot to get a brief insight into “bag of words” of OpenCV. Unfortunately I wasted some time to look into the example from the samples folder in OpenCV (the “bagofwords_classification.cpp”) which I think is a much worse example than yours, because it has over 2500 lines of code with much file handling overhead, actually not necessary to understand the basics of BOW implementation in OpenCV.

   I think it would be of huge value for other people if you could contribute the sources directly into the OpenCV repository (resp. community).
2. Reza

   %A, 13UTCSat, 13 Aug 2011 13:07:51 +0000 %e. %B %Y um %H:%M

   Thanks for your useful topic. After detector->detect(img, keypoint); detects keypoints, when i want to clean keypoints using keypoint.clear(); or when the function wants to return the following error will be appeared.

   “Unhandled exception at 0x011f45bb in BOW.exe: 0xC0000005: Access violation reading location 0x42ebe098.”

   and also detected keypoints have bizarre points coordinates like cv::Point_ pt{x=-1.5883997e+038y=-1.5883997e+038 }

   Part of the code

   Ptr matcher = DescriptorMatcher::create(“FlannBased”);
   Ptr extractor = new SurfDescriptorExtractor();
   Ptr detector = new SurfFeatureDetector(2000);
   void extractTrainingVocabulary() {
   IplImage *img;
   int i,j;
   CvSeq *imageKeypoints = 0;
   for(j=1;j<=60;j++)
   for(i=1;i<=60;i++){
   sprintf( ch,"%d%s%d%s",j," (",i,").jpg");
   const char* imageName = ch;
   Mat img = imread(ch);
   vector keypoint;
   detector->detect(img, keypoint);
   Mat features;
   extractor->compute(img, keypoint, features);
   bowTrainer.add(features);
   keypoint.clear();//problem
   }
   return;
   }