动态验证码源码（详解）

public partial class Admin_RandomImage : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            CreateCheckCode(GetCheckCode());
        }
    }

    //生成随机数
    /// <summary>
    /// 生成随机验证码字符串
    /// </summary>
    /// <returns>生成的随机验证码字符串</returns>
    private string GetCheckCode()
    {
        int number;
        string code = string.Empty;//随机值种子
        Random rd = new Random();
        for (int i = 0; i < 4; i++)//验证码长度是4
        {
            number = rd.Next();
            number = number % 36;
            if (number < 10)
            {
                number += 48;
            }
            else
            {
                number += 55;
            }
            code += ((char)number).ToString();
        }
        Session["CheckCode"] = code;//在session中保存验证码
        return code;
    }

    //画出验证码
    /// <summary>
    /// 根据验证码输出图片
    /// </summary>
    /// <param name="ccode">生成的随机验证码</param>
    private void CreateCheckCode(string ccode)
    {
        //若验证码为空，则直接返回
        if (ccode == null || ccode.Trim() == string.Empty)
        {
            return;
        }
        //根据验证码长度确定输出图片的长度
        System.Drawing.Bitmap image = new System.Drawing.Bitmap(65, 30);
        //创建Graphics对象
        Graphics g = Graphics.FromImage(image);
        try
        {
            //生成随机数种子
            Random rd = new Random();
            //清空图片背景颜色
            g.Clear(Color.White);
            //画图片的背景噪音线10条
            //--------------------------------------------------------------------------
            for (int i = 0; i < 10; i++)
            {
                //噪音线起点坐标（x1,y1），终点坐标（x2,y2）
                int x1 = rd.Next(image.Width);
                int x2 = rd.Next(image.Width);
                int y1 = rd.Next(image.Height);
                int y2 = rd.Next(image.Height);
                //用蓝色画出噪音线
                Pen p = new Pen(Color.Blue);
                g.DrawLine(p, x1, y1, x2, y2);
            }

            //Brush b=Brushes.Silver;
            //g.FillRectangle(b,0,0,image.Width,image.Height);

            //验证码字体：15号Arial，粗斜体，下划线
            Font f = new Font("Arial", 15, (FontStyle.Bold | FontStyle.Italic | FontStyle.Strikeout | FontStyle.Underline));

            //线性渐变画刷
            LinearGradientBrush lgb = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Black, Color.Purple, 1.2f, true);
            g.DrawString(ccode, f, lgb, 2, 2);

            //画图片的前噪音点100个
            for (int i = 0; i < 100; i++)
            {
                int x = rd.Next(image.Width);
                int y = rd.Next(image.Height);
                image.SetPixel(x, y, Color.FromArgb(rd.Next()));
            }
            //画图片的边框线
            g.DrawRectangle(new Pen(Color.Purple), 0, 0, image.Width - 1, image.Height - 1);

            //创建内存流用于输出图片

            using (MemoryStream ms = new MemoryStream())
            {
                //图片类型指定为PNG
                image.Save(ms, ImageFormat.Png);
                //清除缓冲区中的所有输出
                Response.ClearContent();
                //输出流HTTP MIME类型设置为：image/PNG
                Response.ContentType = "image/png";
                //输出图片的二进制流
                Response.BinaryWrite(ms.ToArray());
            }
        }
        finally
        {
            //释放Bitmap对象和Graphics对象
            g.Dispose();
            image.Dispose();
        }
    }

}

动态验证码源码（详解）,布布扣,bubuko.com

动态验证码源码（详解）

原文：http://blog.csdn.net/jin_guang/article/details/22284591