《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