使用的 C# winform

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

        private void Form1_Load(object sender, EventArgs e)
        {
            // 一根筆 繪制直線的對象 pen 顏色 Brush Brushes SolidBrush color  一張紙(圖面) Graphics  兩點 Point

        }

        private void button1_Click(object sender, EventArgs e)
        {
            
 
//創建GDI圖面對象   
            //Graphics g = new Graphics(); 沒有定義構造函數
            //創對象 
            // 1 在堆中開空間 2 在開辟的空間創對象 3 調用構造函數

            Graphics g = this.CreateGraphics();
            //創建畫筆對象  畫筆
            //1
            //Pen pen = new Pen(Brushes.Yellow);//Brush 點不出來 看復數
            //2 直接給筆上色
            Pen pen = new
 
 Pen(Color.Yellow);//
            //Pen pen = new Pen(new Brush(Color.Yellow));Brush 抽象類報錯
            //創建兩個點
            Point p1 = new Point(30, 50);
            Point p2 = new Point(250, 250);

            g.DrawLine(pen, p1, p2);
        }
        int i = 0;
        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            i++;
            label1.Text = i.ToString();
            //創建GDI對象   
            //Graphics g = new Graphics(); 
            //創對象 
            // 1 在堆中開空間 2 在開辟的空間創對象 3 調用構造函數

            Graphics g = this.CreateGraphics();
            //創建畫筆對象  畫筆
            Pen pen = new Pen(Brushes.Yellow);// 復數形式 返回對象
            //創建兩個點
            Point p1 = new Point(30, 50);
            Point p2 = new Point(250, 250);

            g.DrawLine(pen, p1, p2);

        }



        private void button2_Click(object sender, EventArgs e)
        {
            Graphics g = this.CreateGraphics();
            Pen pen = new Pen(Brushes.Yellow);
            Size si = new System.Drawing.Size(80, 80);
            Rectangle rec = new Rectangle(new Point(50, 50), si); // 矩形對象
            g.DrawRectangle(pen, rec);
        }



        private void button3_Click(object sender, EventArgs e)
        {
            Graphics g = this.CreateGraphics();
            Pen pen = new Pen(Brushes.Blue);
            Size si = new System.Drawing.Size(80, 80);
            Rectangle rec = new Rectangle(new Point(100, 100), si);
            g.DrawPie(pen, rec, 60, 60);//他要什麽 我們就給什麽
            //Draw 畫  在圖上繪制 Graphics 

        }

        private void button4_Click(object sender, EventArgs e)
        {
            Graphics g = this.CreateGraphics();
            Font f = new System.Drawing.Font("宋體", 20, FontStyle.Underline);
            g.DrawString("asd520", f, Brushes.Red, new Point(100, 200));
        }
    }
}

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 GDI_驗證碼
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        //點擊更換驗證碼
        private void pictureBox1_Click(object sender, EventArgs e)
        {
            //1 產生隨機數
            Random r = new Random();
            string str = null;
            for (int i = 0; i < 5; i++)
            {
                int rNumber = r.Next(0, 10);
                str += rNumber;
            }
            //MessageBox.Show(str);
            // 畫一個圖片 把文本放到圖片裏面去
            //創建GDI對象
            Bitmap bmp = new Bitmap(150, 40);//創建位圖
            //位圖 操作系統中 默認的圖片類型 其實就是位圖(.bmp)
            Graphics g = Graphics.FromImage(bmp); //對象從圖片來 就是在圖片上繪制

            // 畫數字
            for (int i = 0; i < 5; i++)
            {
                Point p = new Point(i * 20, 0);
                string[] fonts = { "宋體", "微軟雅黑", "黑體", "隸書", "仿宋" };
                Color[] colors = { Color.Yellow, Color.Blue, Color.Red, Color.Black, Color.Green };
                g.DrawString(str[i].ToString(), new Font(fonts[r.Next(0, 5)], 20, FontStyle.Bold), new SolidBrush(colors[r.Next(0, 5)]), p);
            }

            //畫線
            for (int i = 0; i < 20; i++)
            {//線必須在驗證碼圖片裏面
                Point p1 = new Point(r.Next(0, bmp.Width), r.Next(0, bmp.Height));
                Point p2 = new Point(r.Next(0, bmp.Width), r.Next(0, bmp.Height));
                g.DrawLine(new Pen(Brushes.Green), p1, p2);
            }
            //畫點
            for (int i = 0; i < 500; i++)
            {
                //創建點
                Point p = new Point(r.Next(0, bmp.Width), r.Next(0, bmp.Height));
                bmp.SetPixel(p.X, p.Y, Color.Black);//再在圖上畫點
            }


            //將圖片鑲嵌到picturebox中
            pictureBox1.Image = bmp;
        }
    }
}

GDI+ 繪圖教程 驗證碼