First knowledge of opencv4.x --- drawing shapes on images

// Drawing shapes on images 
#include <stdio.h>
#include <iostream>
#include <string>
#include <opencv2\opencv.hpp>
using namespace std;
using namespace cv;

int main()
{
    
	Mat img = Mat::zeros(Size(500, 500), CV_8UC1);// Create a black background , Note that Size(x,y), namely （ Column , That's ok ）
	// A circle 
	circle(img, Point(250,50 ), 30, Scalar(255));// Note that Point(x,y), namely （ Column , That's ok ）
	// Draw a straight line 
	line(img, Point(250, 80), Point(250, 100), Scalar(255));
	line(img, Point(220, 100), Point(200, 150), Scalar(255));
	line(img, Point(280, 100), Point(300, 150), Scalar(255));
	line(img, Point(250, 150), Point(250, 180), Scalar(255));
	line(img, Point(250, 180), Point(220, 200), Scalar(255));
	line(img, Point(250, 180), Point(280, 200), Scalar(255));
	// Draw a rectangular 
	rectangle(img, Point(220, 100), Point(280, 150), Scalar(255));// Draw with two points at the opposite corners of the rectangle 
	// Generate text 
	putText(img, "people", Point(220, 220), 6, 1, Scalar(255));// Currently, only Chinese is supported 
	imshow("img", img);
	waitKey(0);
	return 0;
}