Asp.net验证码
刚做一网站，需要验证码。网上看了好多，自己又改了改，写成下面这个，基于C#
先看下效果：
网站->添加新项->一般处理程序，添加一个名为VerificationCode.ashx的文件。
代码如下：
<%@ WebHandler Language="C#" Class="VerificationCode" %> using System; using System.Web; using System.Drawing; using System.Drawing.Imaging; using System.Text; using System.Web.SessionState; public class VerificationCode : IHttpHandler, IRequiresSessionState /*加上这个接口，否则不能读写Session*/ { #region 私有成员 string code; //验证码 int codeLength = 4; //验证码长度 int width = 70; //图片宽度 int height = 25; //图片高度 int fontSize = 14; //验证码字体大小 static char[] Chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ".ToCharArray(); //字符集 //画刷 static Brush[] BrushItems = new Brush[]{ Brushes.OliveDrab, Brushes.ForestGreen, Brushes.DarkCyan, Brushes.LightSlateGray, Brushes.RoyalBlue, Brushes.SlateBlue, Brushes.DarkViolet, Brushes.MediumVioletRed, Brushes.IndianRed, Brushes.Firebrick, Brushes.Chocolate, Brushes.Peru, Brushes.Goldenrod }; //字体 static string[] FontItems = new string[]{ "Arial", "Helvetica", "Geneva", "sans-serif", "Verdana" }; #endregion public void ProcessRequest (HttpContext context) { context.Response.ContentType = "image/jpeg"; context.Response.Cache.SetCacheability(HttpCacheability.NoCache); //不缓存图片 code = MakeCode(codeLength); //生成验证码 context.Session["VerificationCode"] = code; //将验证码存入Session Bitmap bmp = new Bitmap(width, height); Graphics g = Graphics.FromImage(bmp); DrawBackground(g); //绘制背景 Font font = MakeFont(); Brush brush = MakeBrush(); g.DrawString(code, font, brush, 3, 3); //绘制验证码字符串 DrawStain(bmp,0.08); //绘制噪声点 bmp.Save(context.Response.OutputStream, ImageFormat.Jpeg); } public bool IsReusable { get { return false; } } /// <summary> /// 生成指定位数的随机验证码字符串 /// </summary> /// <param name="length">验证码长度</param> /// <returns>验证码字符串</returns> private string MakeCode(int length) { StringBuilder s = new StringBuilder(); Random r = new Random(); //生成随机字符串 for (int i = 0; i < length; ++i) { int index = r.Next(Chars.Length); s.Append(Chars[index]); } return s.ToString(); } /// <summary> /// 绘制图片背景 /// </summary> /// <param name="g"></param> private void DrawBackground(Graphics g) { g.Clear(Color.White); } /// <summary> /// 在位图中绘制指定比例的噪声点 /// </summary> /// <param name="bmp"></param> /// <param name="percentage">噪声点所占百分比</param> private void DrawStain(Bitmap bmp, double percentage) { int width = bmp.Width; int height = bmp.Height; int n = Convert.ToInt32(width * height * percentage); Random r = new Random(); //随机颜色 int red = r.Next(255); int green = r.Next(255); int blue = r.Next(255); Color color = Color.FromArgb(red,green,blue); for(int i=0;i<n;++i) { //随机坐标 int x = r.Next(1,width); int y = r.Next(1,height); bmp.SetPixel(x, y, color); } } /// <summary> /// 生成随机字体格式（字体、字号、字形） /// </summary> /// <returns></returns> private Font MakeFont() { Random r = new Random(); int i = r.Next(FontItems.Length); string familyName =FontItems[i]; //字体 FontStyle fontStyle = GetFontStyle(r.Next(0,2)); //字形 return new Font(familyName, fontSize, fontStyle); } /// <summary> /// 取得字体样式 /// </summary> /// <param name="index">索引，取值0-2</param> /// <returns></returns> private FontStyle GetFontStyle(int index) { switch (index) { case 0: return FontStyle.Bold; case 1: return FontStyle.Italic; default: return FontStyle.Regular; } } /// <summary> /// 生成随机画刷 /// </summary> /// <returns></returns> private Brush MakeBrush() { Random r = new Random(); int i = r.Next(BrushItems.Length); return BrushItems[i]; } }
生成的验证码存入Session，验证时判断一下即可。
使用时可以用img:
<img alt="验证码" id="imgCode" src="VerificationCode.ashx" onclick="this.src='VerificationCode.ashx?tmp='+new Date().getTime().toString(36);" title="看不清楚，换一张" />
这样可以实现点击图片，刷新验证码的功能。