C# 制作 Windows Forms 图形验证码（带干扰线）

using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
namespace WinFormsCaptcha
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            // 初始化生成验证码
            GenerateCaptchaImage();
        }
        // 生成图形验证码
        private void GenerateCaptchaImage()
        {
            int width = pbCaptcha.Width;
            int height = pbCaptcha.Height;
            // 创建位图
            using (Bitmap bitmap = new Bitmap(width, height))
            using (Graphics g = Graphics.FromImage(bitmap))
            {
                // 设置背景色（浅色）
                g.Clear(Color.AliceBlue);
                // 绘制干扰线（5条随机线）
                Random random = new Random();
                Pen pen = new Pen(Color.LightGray, 1);
                for (int i = 0; i < 5; i++)
                {
                    int x1 = random.Next(width);
                    int y1 = random.Next(height);
                    int x2 = random.Next(width);
                    int y2 = random.Next(height);
                    g.DrawLine(pen, x1, y1, x2, y2);
                }
                // 绘制噪点（100个随机点）
                for (int i = 0; i < 100; i++)
                {
                    int x = random.Next(width);
                    int y = random.Next(height);
                    bitmap.SetPixel(x, y, Color.FromArgb(random.Next(256), random.Next(256), random.Next(256)));
                }
                // 生成4位验证码
                string captcha = GenerateCaptchaText(4);
                // 存储验证码（用于后续验证）
                pbCaptcha.Tag = captcha;
                // 绘制验证码文字（随机字体、颜色、位置）
                Font font = new Font("Arial", 20, FontStyle.Bold | FontStyle.Italic);
                Brush[] brushes = { Brushes.Red, Brushes.Blue, Brushes.Green, Brushes.Orange };
                for (int i = 0; i < captcha.Length; i++)
                {
                    // 每个字符随机颜色、轻微旋转
                    Brush brush = brushes[random.Next(brushes.Length)];
                    float angle = random.Next(-15, 15); // 旋转角度
                    g.TranslateTransform(width / 4 * i + 10, height / 2);
                    g.RotateTransform(angle);
                    g.DrawString(captcha[i].ToString(), font, brush, 0, 0);
                    g.RotateTransform(-angle);
                    g.TranslateTransform(-(width / 4 * i + 10), -height / 2);
                }
                // 设置图片到PictureBox
                pbCaptcha.Image = new Bitmap(bitmap);
            }
        }
        // 生成验证码文本（字母+数字）
        private string GenerateCaptchaText(int length)
        {
            string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
            Random random = new Random();
            char[] captchaChars = new char[length];
            for (int i = 0; i < length; i++)
            {
                captchaChars[i] = chars[random.Next(chars.Length)];
            }
            return new string(captchaChars);
        }
        // 刷新验证码按钮点击事件
        private void btnRefresh_Click(object sender, EventArgs e)
        {
            GenerateCaptchaImage();
        }
        // 验证按钮点击事件（可添加TextBox输入验证）
        private void btnVerify_Click(object sender, EventArgs e)
        {
            string input = txtInput.Text.Trim();
            string captcha = pbCaptcha.Tag.ToString();
            if (string.Equals(input, captcha, StringComparison.OrdinalIgnoreCase))
            {
                MessageBox.Show("验证码正确！", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
            else
            {
                MessageBox.Show("验证码错误！", "提示", MessageBoxButtons.OK, MessageBoxIcon.Error);
                GenerateCaptchaImage(); // 错误后刷新验证码
                txtInput.Clear();
            }
        }
    }
}