影象矩的概念和實際意義可參考https://blog.csdn.net/qq_37207090/article/details/83986950

//計算矩
moments(
InputArray  array,//輸入資料
bool   binaryImage=false // 是否為二值影象
)
//計算面積
contourArea(
InputArray  contour,//輸入輪廓資料
bool   oriented// 預設false、返回絕對值)
//計算長度
arcLength(
InputArray  curve,//輸入曲線資料
bool   closed// 是否是封閉曲線)

步驟
提取影象邊緣
發現輪廓
計算每個輪廓物件的矩

質心座標

例項程式碼

#include <opencv2/opencv.hpp>
#include <iostream>
#include <math.h>

using namespace std;
using namespace cv;

Mat src, gray_src;
int threshold_value = 80;
int threshold_max = 255;
const char* output_win = "image moents demo";
RNG rng(12345);
void
 
 Demo_Moments(int, void*);
int main(int argc, char** argv) {
	src = imread("F:/1.jpg");
	if (!src.data) {
		printf("could not load image...\n");
		return -1;
	}
	cvtColor(src, gray_src, CV_BGR2GRAY);
	GaussianBlur(gray_src, gray_src, Size(3, 3), 0, 0);

	char input_win[] = "input image"
 
;
	namedWindow(input_win, CV_WINDOW_AUTOSIZE);
	namedWindow(output_win, CV_WINDOW_AUTOSIZE);
	imshow(input_win, src);

	createTrackbar("Threshold Value : ", output_win, &threshold_value, threshold_max, Demo_Moments);
	Demo_Moments(0, 0);

	waitKey(0);
	return 0;
}

void Demo_Moments(int, void*) {
	Mat canny_output;
	vector<vector<Point>> contours;
	vector<Vec4i> hierachy;

	Canny(gray_src, canny_output, threshold_value, threshold_value * 2, 3, false);
	findContours(canny_output, contours, hierachy, RETR_TREE, CHAIN_APPROX_SIMPLE, Point(0, 0));

	vector<Moments> contours_moments(contours.size());
	vector<Point2f> ccs(contours.size());
	for (size_t i = 0; i < contours.size(); i++) {
		//計算影象矩
		contours_moments[i] = moments(contours[i]);
		//計算質心座標，static_cast<float>表示型別轉換
		ccs[i] = Point(static_cast<float>(contours_moments[i].m10 / contours_moments[i].m00), static_cast<float>(contours_moments[i].m01 / contours_moments[i].m00));
	}

	Mat drawImg;// = Mat::zeros(src.size(), CV_8UC3);
	src.copyTo(drawImg);
	for (size_t i = 0; i < contours.size(); i++) {
		if (contours[i].size() < 100) {
			continue;
		}
		Scalar color = Scalar(rng.uniform(0, 255), rng.uniform(0, 255), rng.uniform(0, 255));
		printf("center point x : %.2f y : %.2f\n", ccs[i].x, ccs[i].y);
		printf("contours %d area : %.2f   arc length : %.2f\n", i, contourArea(contours[i]), arcLength(contours[i], true));
		drawContours(drawImg, contours, i, color, 2, 8, hierachy, 0, Point(0, 0));
		circle(drawImg, ccs[i], 2, color, 2, 8);
	}

	imshow(output_win, drawImg);
	return;
}