随机验证码

hideCode:

 

using System;
using System.Web;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Web.SessionState;

public class WaterMark : IHttpHandler, IRequiresSessionState  // 要使用session必须实现该接口,记得要导入System.Web.SessionState命名空间
{

    public void ProcessRequest(HttpContext context)
    {
        string checkCode = GenCode(4);  // 产生4位随机字符
        context.Session["RandomCode"] = checkCode; //将字符串保存到Session中，以便需要时进行验证
  
        Bitmap image = new Bitmap(70, 22);
        Graphics g = Graphics.FromImage(image);
        try
        {
            //生成随机生成器
            Random random = new Random();

            //清空图片背景色
            g.Clear(Color.White);

            // 画图片的背景噪音线
            int i;
            for (i = 0; i < 35; i++)
            {
                int x1 = random.Next(image.Width);
                int x2 = random.Next(image.Width);
                int y1 = random.Next(image.Height);
                int y2 = random.Next(image.Height);
                g.DrawLine(new Pen(GetRandomColor()), x1, y1, x2, y2);
             
            }
            Font font = new Font("Arial", 15, FontStyle.Bold | FontStyle.Italic);
            System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2F, true);

            g.SmoothingMode = SmoothingMode.AntiAlias; //指定是否将平滑处理（消除锯齿）应用于直线、曲线和已填充区域的边缘。
            g.Clear(Color.Coral);//清除整个绘图面并以指定背景色填充。
            int rndom = new Random().Next(2);
            g.DrawString(checkCode, font, brush, new PointF(rndom, rndom));

            //画图片的前景噪音点
            for (int j = 0; j < 100; j++)
            {
                int x = random.Next(image.Width);
                int y = random.Next(image.Height);
                image.SetPixel(x, y, Color.Coral);
            }
           
            //画图片的前景噪音点
            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
             System.IO.MemoryStream ms = new System.IO.MemoryStream();
            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
            context.Response.ClearContent();
            context.Response.ContentType = "image/Gif";
            context.Response.BinaryWrite(ms.ToArray());
        }
        finally
        {
            g.Dispose();
            image.Dispose();
        }
    }
 //生成随机颜色
    public Color GetRandomColor()
    {
        Random RandomNum_First = new Random((int)DateTime.Now.Ticks);
        System.Threading.Thread.Sleep(RandomNum_First.Next(50));
        Random RandomNum_Sencond = new Random((int)DateTime.Now.Ticks);
        int int_Red = RandomNum_First.Next(256);
        int int_Green = RandomNum_Sencond.Next(256);
        int int_Blue = (int_Red + int_Green > 400) ? 0 : 400 - int_Red - int_Green;
        int_Blue = (int_Blue > 255) ? 255 : int_Blue;

        return Color.FromArgb(int_Red, int_Green, int_Blue);
    }

    /**/
    /// <summary>
    /// 产生随机字符串
    /// </summary>
    /// <param name="num">随机出几个字符</param>
    /// <returns>随机出的字符串</returns>
    private string GenCode(int num)
    {
        string str = "23456789ABCDEFGHJKLMNPQRSTUVWXYZ";
        char[] chastr = str.ToCharArray();
       
        string code = "";
        Random rd = new Random();
        int i;
        for (i = 0; i < num; i++)
        {
            code += str.Substring(rd.Next(0, str.Length), 1);
        }
        return code;

    }

    public bool IsReusable
    {
        get
        {
            return true;
        }
    }

}

前台引用：

      //更新验证码
       function change()
        {   
            var imgNode = document.getElementById("vimg");  
            imgNode.src = "WaterMark.ashx?t=" + (new Date()).valueOf();  // 这里加个时间的参数是为了防止浏览器缓存的问题  
        } 

       <img src="WaterMark.ashx" id="vimg" onclick="change()" style="cursor: hand; margin-bottom: 0;"  height="22" title="点击刷新验证码" />