练习1

代码

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApp17
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            //创建Graphics对象
            Graphics GPS = this.CreateGraphics();
            //创建黑色pen对象
            Pen MyPen = new Pen(Color.Black, 2f);
            //确定起点和终点
            Point pt1 = new Point(270, 100);
            Point pt2 = new Point(270, 150);
            //使用DrawLine方法绘制直线
            GPS.DrawLine(MyPen, pt1, pt2);
            //改变坐标原点为第一个点
            
            GPS.TranslateTransform(270,100);
            //每隔15度
            int angle = 15;
            for (int i = 0; i <= 9; ++i)
            {
                
                GPS.RotateTransform(angle);
                GPS.DrawLine(MyPen, 0, 0, 300, 20);
                                
            }
            
        }
    }
}

运行结果

AfterRun.PNG

练习2

代码

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Drawing.Drawing2D;

namespace WindowsFormsApp18
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Paint(object sender, PaintEventArgs e)
        {

            Graphics g = this.CreateGraphics();
            Point center = new Point(200, 100);
            int radius = 80;
            Point[] pts = new Point[5];
            //获取五角星5个顶点
            pts[0] = new Point(center.X, center.Y - radius);
            pts[1] = Rotate72(pts[0], center);
            pts[2] = Rotate72(pts[1], center);
            pts[3] = Rotate72(pts[2], center);
            pts[4] = Rotate72(pts[3], center);
            //简单地拉5条线
            Pen pen = new Pen(new SolidBrush(Color.Red));
            g.DrawLine(pen, pts[0], pts[2]);
            g.DrawLine(pen, pts[0], pts[3]);
            g.DrawLine(pen, pts[1], pts[3]);
            g.DrawLine(pen, pts[1], pts[4]);
            g.DrawLine(pen, pts[2], pts[4]);
            /*
            Point vOrigin = new Point(100, 100); // 圆心
            int vRadius = 70; // 半径
            Point[] vPoints = new Point[5];
            double vAngle = 2.0 * Math.PI / 4 + Math.PI;
            for (int i = 0; i < vPoints.Length; i++)
            {
                vAngle += 2.0 * Math.PI / (double)vPoints.Length;
                vPoints[i] = new Point(
                    (int)(Math.Cos(vAngle) * vRadius) + vOrigin.X,
                    (int)(Math.Sin(vAngle) * vRadius) + vOrigin.Y);
            }
            e.Graphics.DrawPolygon(Pens.Blue, vPoints);
            for (int i = 0; i < vPoints.Length; i++)
            {
                vPoints[i].Offset(150, 0);
            }
            Point[] vTemps = new Point[vPoints.Length];
            vTemps[0] = vPoints[0];
            vTemps[1] = vPoints[2];
            vTemps[2] = vPoints[4];
            vTemps[3] = vPoints[1];
            vTemps[4] = vPoints[3];
            e.Graphics.DrawPolygon(Pens.Red, vTemps);
        }
        */
                

        }

        //旋转72度
        private Point Rotate72(Point pt, Point center)
        {
            int x = (int)(center.X + (pt.X - center.X) * Math.Cos(72.0 * Math.PI / 180) - (pt.Y - center.Y) * Math.Sin(72.0 * Math.PI / 180)),
            y = (int)(center.Y + (pt.X - center.X) * Math.Sin(72.0 * Math.PI / 180) + (pt.Y - center.Y) * Math.Cos(72.0 * Math.PI / 180));
            return new Point(x, y);
        }
    }
}

运行结果

AfterRun.PNG

练习3

代码

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApp1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        SolidBrush SB;//定义单色画刷
        Graphics g;
        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            switch(comboBox1.SelectedIndex)
            {
                case 0:
                    {
                        //填充矩形
                        g.Clear(BackColor);//通过清除背景达到清除之前的图形的目的
                        Rectangle myR = new Rectangle(40, 60, 400, 200);
                        g.FillRectangle(SB, myR);
                        break;
                    }
                case 1:
                    {
                        //填充多边形
                        //定义多边形顶点
                        g.Clear(BackColor);//通过清除背景达到清除之前的图形的目的
                        Point pt1 = new Point(90, 30);
                        Point pt2 = new Point(50, 60);
                        Point pt3 = new Point(90, 90);
                        Point pt4 = new Point(170, 90);
                        Point pt5 = new Point(210, 60);
                        Point pt6 = new Point(170, 30);
                        //定义point结构数组，用来表示多边形的点
                        Point[] curvePoints = { pt1, pt2, pt3, pt4, pt5, pt6 };
                        g.FillPolygon(SB, curvePoints);
                        break;
                    }
                default:
                    {
                        g.Clear(BackColor);//通过清除背景达到清除之前的图形的目的
                        Rectangle Rec = new Rectangle(40, 60, 70, 70);
                        g.FillEllipse(SB, Rec);
                        break;
                    }
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            SB = new SolidBrush(Color.Red);//创建单色画刷对象
            g = this.CreateGraphics();//创建Graphics对象
        }
    }
}

运行结果

AfterRun3.PNG

AfterRun2.PNG

AfterRun.PNG