opencv
Blob-Erkennung

Kreisförmige Blob-Erkennung

Dieses Beispiel zeigt, wie Sie kreisförmige Flecken in einem Graustufenbild finden. Die Bewertung der Zirkularität eines Flecks erfolgt anhand der Fläche und des Umfangs (Bogenlänge) der Kontur. Der Mittelpunkt wird anhand der Momente der Kontur ausgewertet.

#include "opencv/cv.h"
#include "opencv/highgui.h"
#include "opencv/cxcore.h"

using namespace cv;

int main(int argc, char** argv)
{
    Mat img = imread("image.jpg", CV_LOAD_IMAGE_GRAYSCALE);
    Mat resultImg;
    cvtColor(img, resultImg, CV_GRAY2BGR);

    // threshold the image with gray value of 100
   Mat binImg;
   threshold(img, binImg, 100, 255, THRESH_BINARY);

    // find the contours
    vector<vector<Point>> contours;
    vector<Vec4i> hierarchy;
    findContours(binImg, contours, hierarchy, CV_RETR_CCOMP, CV_CHAIN_APPROX_SIMPLE);

    if(contours.size() <= 0)
    {
        printf("no contours found");
        return 0;
    }
    // filter the contours
    vector<vector<Point>> filteredBlobs;
    Mat centers = Mat::zeros(0,2,CV_64FC1);
    for(int i = 0; i < contours.size(); i++)
    {
        // calculate circularity
        double area = contourArea(contours[i]);
        double arclength = arcLength(contours[i], true);
        double circularity = 4 * CV_PI * area / (arclength * arclength);
        if(circularity > 0.8)
        {
            filteredBlobs.push_back(contours[i]);
        
            //calculate center
            Moments mu = moments(contours[i], false);
            Mat centerpoint = Mat(1,2,CV_64FC1);
            centerpoint.at<double>(i,0) = mu.m10 / mu.m00; // x-coordinate
            centerpoint.at<double>(i,1) = mu.m01 / mu.m00; // y-coordinate
            centers.push_back(centerpoint);
        }
    }

    if(filteredBlobs.size() <= 0)
    {
        printf("no circular blobs found");
        return 0;
    }
    drawContours(resultImg, filteredBlobs, -1, Scalar(0,0,255), CV_FILLED, 8);

    imshow("Blobs",resultImg);
    waitKey(0);
    return 0;
}