Label Value discontinuous

[tomicfish]

the code:
`
//TestDLL.c : test of CvBlob DLL

cv::Mat img = cv::imread("test.png", 1);
cv::Mat grey;
grey.create(img.size(), CV_8UC1);
cv::cvtColor(img, grey, CV_BGR2GRAY, 1);
cv::threshold(grey, grey, 0, 255, CV_THRESH_BINARY + CV_THRESH_OTSU);    
LARGE_INTEGER freq;
LARGE_INTEGER t0, tF, tDiff;
double elapsedTime;

// cvblob
QueryPerformanceFrequency(&freq);
QueryPerformanceCounter(&t0);

cvb::BlobList blobs;
cvb::Label max_label = 250;
blobs.SimpleLabel(grey, max_label);
blobs.FilterByArea(10, img.cols * img.rows);

QueryPerformanceCounter(&tF);
tDiff.QuadPart = tF.QuadPart - t0.QuadPart;
elapsedTime = tDiff.QuadPart / (double) freq.QuadPart;
std::cout << "cvblob:" << elapsedTime << std::endl;

for (auto &a_blob : blobs.get_BlobsList()) {
    // extract and draws blob contour
    auto contours = a_blob->get_Contour().get_ContourPolygon();
    if (contours.size() != 1) {
        for (auto &iter = contours.begin(); iter != contours.end(); iter++) {
            auto next_iter = iter;
            next_iter++;
            if (next_iter == contours.end())
                cv::line(img, *iter, contours[0], cv::Scalar(0, 0, 255), 1, 8);
            else
                cv::line(img, *iter, *next_iter, cv::Scalar(0, 0, 255), 1, 8);
        }
    }

    // extract and draws every blob internal hole contour
    auto internal_contours = a_blob->get_InternalContours();
    for (auto &a_contour : internal_contours) {
        auto contour_dot = a_contour->get_ContourPolygon();
        if (contour_dot.size() == 1)
            continue;
        for (auto &iter = contour_dot.begin(); iter != contour_dot.end(); iter++) {
            auto next_iter = iter;
            next_iter++;
            if (next_iter == contour_dot.end())
                cv::line(img, *iter, contour_dot[0], cv::Scalar(0, 255, 0), 1, 8);
            else
                cv::line(img, *iter, *next_iter, cv::Scalar(0, 255, 0), 1, 8);
        }
    }

    // draws bounding box
    cv::rectangle(img, a_blob->get_BoundingBox(), cv::Scalar(255, 0, 255));

    // draws centroid
    cv::circle(img, a_blob->get_Centroid(), 2, cv::Scalar(255, 0, 0), 2);
};

cv::imwrite("imggray.png", grey);
cv::imwrite("imgout.png", img);
cv::Mat labeImgTemp = blobs.get_ImageLabel() *24;
cv::imwrite("imglabelMat.png", labeImgTemp);
return 0;

`
In the picture(imglabelMat.png), the label values are discontinuous.
imglabelMat.png:

imggray.png:

imgout.png: