如何用鼠标点击在picturebox的图像上做标记

鼠标点击图像，在点击处画一个圆。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
 
namespace PictureDemo
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
 
        private void pictureBox1_Click(object sender, EventArgs e)
        {
            //得到鼠标相对于pictureBox左上角的位置
            Point p1=pictureBox1.PointToClient(Control.MousePosition);
 
 
            Image imageBmp = pictureBox1.Image;
            using (Graphics g = Graphics.FromImage(imageBmp))
            {
                g.SmoothingMode = SmoothingMode.AntiAlias;         //抗锯齿
                g.PixelOffsetMode = PixelOffsetMode.HighQuality;   //高质量
                g.InterpolationMode = InterpolationMode.High;      //差值算法
 
                Color penColor = Color.Green;
                Pen pens = new Pen(penColor, 1);                //定义画笔(线条)
                Brush brushs = new SolidBrush(penColor);        //定义画刷(填充)
                g.DrawEllipse(pens, p1.X, p1.Y, 50, 50);//画圆弧线条
                g.FillEllipse(brushs, p1.X, p1.Y, 50, 50);//填充圆弧
            }
            pictureBox1.Image = imageBmp;
 
                        
        }
    }
}