the centroid of vessels opencv - c++

Question

I have this image the vascular bundle
My work is to find the centroid of the blood vessels ,
I tried Image moments but I have this error message error
My code is here:
int main() {
cv::Mat img = imread("C:\\Users\\ASUS\\Desktop\\fond1.png ", CV_LOAD_IMAGE_COLOR);
Mat blue, green, red, step1, otsu, step11, green1, blue1;
Mat bgr[3]; //destination array
split(img, bgr);//split source
red.push_back(bgr[2]);
Moments mu = moments(red,true);
Point center;
center.x = mu.m10 / mu.m00;
center.y = mu.m01 / mu.m00;
circle(red, center, 2, Scalar(0, 0, 255));
imshow("Result",red);
Mat mask(red.size(), CV_8UC1, Scalar::all(0));
// Create Polygon from vertices
vector<Point> ROI_Vertices(3);
ROI_Vertices.push_back(Point(0,0 ));
ROI_Vertices.push_back(Point(center.x, center.y));
ROI_Vertices.push_back(Point(0,red.rows -1));
vector<Point> ROI_Poly;
approxPolyDP(ROI_Vertices, ROI_Poly, 1.0, true);
// Fill polygon white
fillConvexPoly(mask, &ROI_Poly[0], ROI_Poly.size(), 255, 8, 0);
Mat hide(red.size(), CV_8UC3);
red.copyTo(hide, mask);
imshow("mask", hide);
Mat blackhat,tophat,dst;
Mat element = getStructuringElement(MORPH_ELLIPSE, Size(6,6));
morphologyEx(hide, blackhat, MORPH_BLACKHAT, element);
imshow("step1", blackhat);
morphologyEx(blackhat, tophat, MORPH_TOPHAT, element);
imshow("step2", tophat);
cv::Mat r1 = cv::Mat::zeros(dst.rows, dst.cols, CV_8UC1);
tophat.copyTo(r1);
imshow("vessel", r1);
threshold(r1, dst, 9, 255, THRESH_BINARY);
// Find contours
vector<vector<Point>> contours;
vector<Vec4i> hierarchy;
///Get the moments
Mat canny_output;
// detect edges using canny
Canny(dst, canny_output, 50, 150, 3);
// find contours
findContours(canny_output, contours, hierarchy, RETR_TREE, CHAIN_APPROX_SIMPLE, Point(0, 0));
// get the moments
vector<Moments> mu(contours.size());
for (int i = 0; i<contours.size(); i++)
{
mu[i] = moments(contours[i], false);
}
// get the centroid of figures.
vector<Point2f> mc(contours.size());
for (int i = 0; i<contours.size(); i++)
{
mc[i] = Point2f(mu[i].m10 / mu[i].m00, mu[i].m01 / mu[i].m00);
}