Blob tracking algorithm

Question

I\'m trying to create simple blob tracking using OpenCV. I have detected the blobs using findcontours. I would like to give those blobs a constant ID.

I have collec

Answer 1

Here's a OpenCV code sample of blob tracking:

#include "stdafx.h"

#include 

IplImage* GetThresholdedImage(IplImage* img)
{
    // Convert the image into an HSV image
    IplImage* imgHSV = cvCreateImage(cvGetSize(img), 8, 3);
    cvCvtColor(img, imgHSV, CV_BGR2HSV);

    IplImage* imgThreshed = cvCreateImage(cvGetSize(img), 8, 1);

    // Values 20,100,100 to 30,255,255 working perfect for yellow at around 6pm
    cvInRangeS(imgHSV, cvScalar(112, 100, 100), cvScalar(124, 255, 255), imgThreshed);

    cvReleaseImage(&imgHSV);

    return imgThreshed;
}

int main()
{
    // Initialize capturing live feed from the camera
    CvCapture* capture = 0;
    capture = cvCaptureFromCAM(0);  

    // Couldn't get a device? Throw an error and quit
    if(!capture)
    {
        printf("Could not initialize capturing...\n");
        return -1;
    }

    // The two windows we'll be using
    cvNamedWindow("video");
    cvNamedWindow("thresh");

    // This image holds the "scribble" data...
    // the tracked positions of the ball
    IplImage* imgScribble = NULL;

    // An infinite loop
    while(true)
    {
        // Will hold a frame captured from the camera
        IplImage* frame = 0;
        frame = cvQueryFrame(capture);

        // If we couldn't grab a frame... quit
        if(!frame)
            break;

        // If this is the first frame, we need to initialize it
        if(imgScribble == NULL)
        {
            imgScribble = cvCreateImage(cvGetSize(frame), 8, 3);
        }

        // Holds the yellow thresholded image (yellow = white, rest = black)
        IplImage* imgYellowThresh = GetThresholdedImage(frame);

        // Calculate the moments to estimate the position of the ball
        CvMoments *moments = (CvMoments*)malloc(sizeof(CvMoments));
        cvMoments(imgYellowThresh, moments, 1);

        // The actual moment values
        double moment10 = cvGetSpatialMoment(moments, 1, 0);
        double moment01 = cvGetSpatialMoment(moments, 0, 1);
        double area = cvGetCentralMoment(moments, 0, 0);

        // Holding the last and current ball positions
        static int posX = 0;
        static int posY = 0;

        int lastX = posX;
        int lastY = posY;

        posX = moment10/area;
        posY = moment01/area;

        // Print it out for debugging purposes
        printf("position (%d,%d)\n", posX, posY);

        // We want to draw a line only if its a valid position
        if(lastX>0 && lastY>0 && posX>0 && posY>0)
        {
            // Draw a yellow line from the previous point to the current point
            cvLine(imgScribble, cvPoint(posX, posY), cvPoint(lastX, lastY), cvScalar(0,255,255), 5);
        }

        // Add the scribbling image and the frame... and we get a combination of the two
        cvAdd(frame, imgScribble, frame);
        cvShowImage("thresh", imgYellowThresh);
        cvShowImage("video", frame);

        // Wait for a keypress
        int c = cvWaitKey(10);
        if(c!=-1)
        {
            // If pressed, break out of the loop
            break;
        }

        // Release the thresholded image... we need no memory leaks.. please
        cvReleaseImage(&imgYellowThresh);

        delete moments;
    }

    // We're done using the camera. Other applications can now use it
    cvReleaseCapture(&capture);
    return 0;
}