MikeStrike's profile - activity

I want to set up an object detection based on camera images. The idea is that I start with an empty database and subsequently add objects into it with the camera. So far I have a tracking algorithm (https://code.google.com/p/opencv-cookbook/source/browse/trunk/Chapter%2010/featuretracker.h?r=2) (modified but basically the same).

What I am now not sure about is, how to set up the database.

The idea is the following:

I am detecting SIFT feature points (lets say frame1 1000 FeaturePoints(FPs)) in the first frame. In the subsequent frame2 I am taking over the features I recognized in frame1 due to the tracking algorithm (say 500). With this 500 I go to frame3 and take over those FPs I can track from frame2 (say 400) and so on. This means that the number of feature points in constantly dropping over the frames.

Similar to the Algorithm I want to introduce two thresholds of say 100FPs and 40FPs. If I undergo 100Fps (assume this happens in frame6) - then I start to detect again SIFT features in frame6 and push the points with that back to 1000. Unless the drop is so high that I do not only undergo 100 FPs but also 40FPs in frame6 then I consider this frame to show a new Object.

Let's say I have to refresh my FPs every 6 frames and after 7 refreshs I drop below 40 and want to classify the object. This means I have recognized 7000 Fps for Object 1. But many of them are very similar or even the same. Therefore I thought about putting this FPs into an SVM to learn the object. Now the question is what kind of SVM is the best for my purpose. I cannot do a "negative training", means I have no images which are showing the wrong object to train the classifier. I could do that once I have detected a few objects.

Additionally I want to save my results on the hard disk so that I can load them and proceed another time learning/matching other objects.

I hope my problem became clear and somebody can give me inspiration or good advice how to proceed.

Best Regards

Hello,

I use the following feature tracker: https://code.google.com/p/opencv-cookbook/source/browse/trunk/Chapter%2010/featuretracker.h?r=2

What I do not understand is how it works with the in-/output point positions in the images. If there is no prev. Image, the algorithm stores the current image (gray) in (gray_prev) and then calls

 cv::calcOpticalFlowPyrLK(gray_prev, gray, // 2 consecutive images
                        points[0], // input point position in first image
                        points[1], // output point postion in the second image
                        status,    // tracking success
                        err);      // tracking error

In the first iteration gray_prev and gray are the same and therefore all points in points[0] can be copied to points[1] - fine. Then the algrithm kicks out some points in points[1] and swaps gray_prev and gray respectively points[1] and points[0].

Which means that in the next iteration - right after calling the processing method, the keypoints in points[0] correspond to the previus frame ( gray_prev ). Now, if the number of points in points[0] is to low, new keypoints - which were found in the current image (gray) - are added

                        points[0].insert(points[0].end(),features.begin(),features.end());
                        initial.insert(initial.end(),features.begin(),features.end());

This means that we mix keypoints from both images in points[0]?! How does this work?

Thank you very much, that was the reason!

Hi,

I get the error message mentioned above when I try to compile the following (extract from my VideoProcessor.cpp file):

...

    void VideoProcessor::run() {

                  // current frame
                  cv::Mat frame;
                  // output frame
                  cv::Mat output;

                  // if no capture device has been set
                  if (!isOpened())
                          return;

                  stop= false;

                  while (!isStopped()) {

//                           read next frame if any
                          if (!readNextFrame(frame))
                                  break;

                          // display input frame
                          if (windowNameInput.length()!=0)
                                  cv::imshow(windowNameInput,frame);

                      // calling the process function or method
                          if (callIt) {

                                // process the frame
                                if (process)
                                    process(frame, output);
                                else if (frameProcessor)
                                        frameProcessor->process(frame,output);
                                // increment frame number
                            fnumber++;

                          } else {

                                output= frame;
                          }

                          // write output sequence
                          if (outputFile.length()!=0)
                                  writeNextFrame(output);

                          // display output frame
                          if (windowNameOutput.length()!=0)
                                  cv::imshow(windowNameOutput,output);

                          // introduce a delay
                          if (delay>=0 && cv::waitKey(delay)>=0)
                                stopIt();

                          // check if we should stop
                          if (frameToStop>=0 && getFrameNumber()==frameToStop)
                                  stopIt();
                  }
          }

...

The two error messages say:

1. undefined reference to 'VideoProcessor::readNextFrame(cv::Mat&)'
2. undefined reference to 'VideoProcessor::writeNextFrame(cv::Mat&)'

while the corresponding header file looks the like that:

...

private:

bool readNextFrame(cv::Mat& frame);

void writeNextFrame(cv::Mat& frame);

public:

...

void run();

...

I included the header file and all other methods in this class work very well.

Thanks

thank you very much! It works now :).

Thanks for the quick reply! BuildInformation() gave me the following: with getBuildInformation()

Video I/O: OpenNI: NO OpenNI PrimeSensor Modules: NO

sorry for the stupid question, but does that mean it is not supported or just no activated? And when I reinstall opencv, do I have to uninstall the current version first or can I just rebuild it using cmake?

Hi,

I am trying to make the Asus Xtion pro live work with my computer. I am using ubuntu 12.04 with Opencv 2.4.6.1. I have been trying this for quite some time now but I cannot make it work.

I downloaded the the tools from http://www.asus.com/Multimedia/Xtion_PRO_LIVE/#support_Download_5 a. PrimeSense Software Package 20.4.2.20 ： 1. OpenNI Framework (Version 1.5.2.23) 2. Sensor DDK (version 5.1.0.41) 3. NITE (version 1.5.2.21) 4. USB driver (version 3.1.3.1)

Then I followed the installation instructions and tried to run the Xtion in NiViewer, which works fine. After that I wanted to make the example code on http://docs.opencv.org/doc/user_guide/ug_highgui.html run.

But when I try to run the code, I get the the error Message "Can not open a capture object", which is cause by

if( isVideoReading )
        capture.open( filename );
    else
        capture.open(CV_CAP_OPENNI );

    cout << "done." << endl;

    if( !capture.isOpened() )
    {
        cout << "Can not open a capture object." << endl;
        return -1;
    }

This is what is mentioned in 2. on http://docs.opencv.org/doc/user_guide/ug_highgui.html. How can I change the CMake variables in Codeblocks? I have no CMakeLists.txt as I just created an empty project and added a .cpp file.

Thanks!