《学习OpenCV(中文版)》

作者：（美）布拉德斯基（Bradski，G.）
（美）克勒（Kaehler，A.） 著
出版社：清华大学出版社
出版时间：2009年10月

https://zhidao.baidu.com/question/2073567152212492428.html

一、五角星

已知五角星的外接圆半径r，如何求五角星十个顶点的坐标？

如图，

A（rcos18°，rsin18°）

B（rcos90°，rsin90°）

C（rcos162°，rsin162°）

D（rcos234°，rsin234°）

E（rcos306°，rsin306°）

OF=rsin18°/sin126°=r'

F（r'cos54°，r'sin54°）

G（r'cos126°，r'sin126°）

H（r'cos198°，r'sin198°）

I（r'cos270°，r'sin272°）

J（r'cos342°，r'sin342°）

二、动态绘制五角星

namespace Ky_CvRoi
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        public string SourceFname = @"d:\2022视觉文件夹\安柏.JPG";
        public Mat S0 = Cv2.ImRead(@"d:\2022视觉文件夹\安柏.JPG", ImreadModes.Unchanged);
        public OpenCvSharp.Point p1 = new OpenCvSharp.Point(-1, -1);
        public OpenCvSharp.Point p2 = new OpenCvSharp.Point(-1, -1);
        bool mouseDown = false; 

        #region  定义一个发送接收图像数据的全局变量SendPicData
        public Mat SendPicData  
        {
            get { return BitmapConverter.ToMat((Bitmap)pictureBox1.Image); }
            set { pictureBox1.Image = value.ToBitmap(); }
        }
        #endregion


        private void Form1_Load(object sender, EventArgs e)
        {
            pictureBox1.Image = S0.ToBitmap();
            
        }

        private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            mouseDown = true;
            if (mouseDown)
            {
                p1.X = e.X;
                p1.Y = e.Y;
                textBox1.Text = textBox1.Text + "p1=(" + e.X.ToString() + " , " + e.Y.ToString() + ")\r\n";
            }
        }


        private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            OpenCvSharp.Point p0;
            mouseDown = false;
                int w1=0;
                int h1=0;
                if ((p1.X >= 0) && (p1.Y >= 0))
                {
                    p2.X = e.X;
                    p2.Y = e.Y;
                    textBox1.Text = textBox1.Text + "p2=(" + e.X.ToString() + " , " + e.Y.ToString() + ")\r\n";
                    w1 = p2.X - p1.X;
                    h1 = p2.Y - p1.Y;
                    if (p2.X < p1.X)
                    {
                        w1 = p1.X - p2.X;
                    };
                    if (p2.Y < p1.Y)
                    {
                        h1 = p1.Y - p2.Y;
                    }
                }

                OpenCvSharp.Scalar scalar = new OpenCvSharp.Scalar(0, 200, 200);
            // 画矩形
            //S0.Rectangle(p1, p2, scalar,2);
            // 画圆
      
            p0.X = (p1.X + p2.X) / 2;
            p0.Y = (p1.Y + p2.Y) / 2;
            int r0 = 0;
            r0 = (int) (w1/2);  
            S0.Circle(p0, r0, scalar,2);
            pictureBox1.Image = OpenCvSharp.Extensions.BitmapConverter.ToBitmap(S0);
            // 画五角星

            p0.X = (p1.X + p2.X) / 2;
            p0.Y = (p1.Y + p2.Y) / 2;
            int r;
            r0=(int)(w1 / 2);
            int r1 =(int)( r0 * Math.Sin(Math.PI / 10) / Math.Sin(Math.PI * 7 / 10));

            List<OpenCvSharp.Point> pts1 = new List<OpenCvSharp.Point>
                {
                new OpenCvSharp.Point((int)p0.X+r0*Math.Cos(Math.PI/10),(int)p0.Y-r0*Math.Sin(Math.PI/10)),
                new OpenCvSharp.Point((int)p0.X+r1*Math.Cos(Math.PI*3/10),(int) p0.Y-r1*Math.Sin(Math.PI*3/10)),
                new OpenCvSharp.Point((int)p0.X+r0*Math.Cos(Math.PI*5/10),(int) p0.Y-r0*Math.Sin(Math.PI*5/10)),
                new OpenCvSharp.Point((int)p0.X+r1*Math.Cos(Math.PI*7/10),(int) p0.Y-r1*Math.Sin(Math.PI*7/10)),
                new OpenCvSharp.Point((int)p0.X+r0*Math.Cos(Math.PI*9/10),(int) p0.Y-r0*Math.Sin(Math.PI*9/10)),
                new OpenCvSharp.Point((int)p0.X+r1*Math.Cos(Math.PI*11/10),(int) p0.Y-r1*Math.Sin(Math.PI*11/10)),
                new OpenCvSharp.Point((int)p0.X+r0*Math.Cos(Math.PI*13/10),(int) p0.Y-r0*Math.Sin(Math.PI*13/10)),
                new OpenCvSharp.Point((int)p0.X+r1*Math.Cos(Math.PI*15/10), (int)p0.Y-r1*Math.Sin(Math.PI*15/10)),
                new OpenCvSharp.Point((int)p0.X+r0*Math.Cos(Math.PI*17/10),(int) p0.Y-r0*Math.Sin(Math.PI*17/10)),
                new OpenCvSharp.Point((int)p0.X+r1*Math.Cos(Math.PI*19/10), (int)p0.Y-r1*Math.Sin(Math.PI*19/10))
                    };

            List<List<OpenCvSharp.Point>> pts = new List<List<OpenCvSharp.Point>>() { pts1 };
            //画五角星
            Cv2.Polylines(S0, pts, true, new Scalar(0, 0, 255), 2);

            pictureBox1.Image = OpenCvSharp.Extensions.BitmapConverter.ToBitmap(S0);

        }

        private void button2_Click(object sender, EventArgs e)
        {
            string path = @"d:\2022视觉文件夹\安柏.JPG";
            pictureBox1.Image = new Bitmap(path);

            S0 = new Mat(path);
            pictureBox1.Image = OpenCvSharp.Extensions.BitmapConverter.ToBitmap(S0);
        }
    }
}

三、运行结果