红马版验证码实现(中文+变形+噪点)
为了应付越来越多的自动发帖机、恶意攻击等情形,验证码技术在大量的网站上得到使用。我在近期开发一个注册网站的时候,也使用了这一技术。当然,我并不想完完全全自己重新实现,而是参考了网上能够找到的实现,做了若干改进而已。下面谈谈我的实现。
补两张图片:
首先看验证码图片输出页的代码:
<%@ Page Language="C#" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <script runat="server"> protected void Page_Load(object sender, EventArgs e) { VryImgGen gen = new VryImgGen(); string verifyCode = gen.CreateVerifyCode(5, 1); Session["VerifyCode"] = verifyCode.ToUpper(); System.Drawing.Bitmap bitmap = gen.CreateImage(verifyCode); System.IO.MemoryStream ms = new System.IO.MemoryStream(); bitmap.Save(ms, System.Drawing.Imaging.ImageFormat.Png); Response.Clear(); Response.ContentType = "image/Png"; Response.BinaryWrite(ms.GetBuffer()); bitmap.Dispose(); ms.Dispose(); ms.Close(); Response.End(); } </script>
功能很简单,初始化一个验证码生成对象,生成图片。然后保存到一个MemoryStream里。得到字节流,输出字节流。验证码的数据是保存在Session中的,这是最简单的方法。或者可以加密储存在cookie里,也是可以的。
再来看看验证码生成对象:
using System; using System.Data; using System.Configuration; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Web.UI.HtmlControls; using System.Drawing; using System.Text; /// <summary> /// Summary description for VryImgGen /// </summary> public partial class VryImgGen { /// <summary> /// 供验证码生成汉字时选取的汉字集,若为空则按照《GB2312简体中文编码表》编码规则构造汉字 /// </summary> public static string ChineseChars = String.Empty; /// <summary> /// 英文与数字串 /// </summary> protected static readonly string EnglishOrNumChars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"; public VryImgGen() { rnd = new Random(unchecked((int)DateTime.Now.Ticks)); } /// <summary> /// 全局随机数生成器 /// </summary> private Random rnd; int length = 5; /// <summary> /// 验证码长度(默认6个验证码的长度) /// </summary> public int Length { get { return length; } set { length = value; } } int fontSize = 18; /// <summary> /// 验证码字体大小(为了显示扭曲效果,默认30像素,可以自行修改) /// </summary> public int FontSize { get { return fontSize; } set { fontSize = value; } } int padding = 4; /// <summary> /// 边框补(默认4像素) /// </summary> public int Padding { get { return padding; } set { padding = value; } } bool chaos = true; /// <summary> /// 是否输出燥点(默认输出) /// </summary> public bool Chaos { get { return chaos; } set { chaos = value; } } Color chaosColor = Color.LightGray; /// <summary> /// 输出燥点的颜色(默认灰色) /// </summary> public Color ChaosColor { get { return chaosColor; } set { chaosColor = value; } } Color backgroundColor = Color.White; /// <summary> /// 自定义背景色(默认白色) /// </summary> public Color BackgroundColor { get { return backgroundColor; } set { backgroundColor = value; } } Color[] colors = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple }; /// <summary> /// 自定义随机颜色数组 /// </summary> public Color[] Colors { get { return colors; } set { colors = value; } } string[] fonts = { "Arial", "Georgia" }; /// <summary> /// 自定义字体数组 /// </summary> public string[] Fonts { get { return fonts; } set { fonts = value; } }
#region 产生波形滤镜效果
private const double PI = 3.1415926535897932384626433832795; private const double PI2 = 6.283185307179586476925286766559; /// <summary> /// 正弦曲线Wave扭曲图片(Edit By 51aspx.com) /// </summary> /// <param name="srcBmp">图片路径</param> /// <param name="bXDir">如果扭曲则选择为True</param> /// <param name="nMultValue">波形的幅度倍数,越大扭曲的程度越高,一般为3</param> /// <param name="dPhase">波形的起始相位,取值区间[0-2*PI)</param> /// <returns></returns> public System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase) { System.Drawing.Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height); // 将位图背景填充为白色 System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(destBmp); graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), 0, 0, destBmp.Width, destBmp.Height); graph.Dispose(); double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width; for (int i = 0; i < destBmp.Width; i++) { for (int j = 0; j < destBmp.Height; j++) { double dx = 0; dx = bXDir ? (PI2 * (double)j) / dBaseAxisLen : (PI2 * (double)i) / dBaseAxisLen; dx += dPhase; double dy = Math.Sin(dx); // 取得当前点的颜色 int nOldX = 0, nOldY = 0; nOldX = bXDir ? i + (int)(dy * dMultValue) : i; nOldY = bXDir ? j : j + (int)(dy * dMultValue); System.Drawing.Color color = srcBmp.GetPixel(i, j); if (nOldX >= 0 && nOldX < destBmp.Width && nOldY >= 0 && nOldY < destBmp.Height) { destBmp.SetPixel(nOldX, nOldY, color); } } } return destBmp; }
#endregion
/// <summary> /// 生成校验码图片 /// </summary> /// <param name="code">验证码</param> /// <returns></returns> public Bitmap CreateImage(string code) { int fSize = FontSize; int fWidth = fSize + Padding; int imageWidth = (int)(code.Length * fWidth) + 4 + Padding * 2; int imageHeight = fSize * 2 + Padding * 2; System.Drawing.Bitmap image = new System.Drawing.Bitmap(imageWidth, imageHeight); Graphics g = Graphics.FromImage(image); g.Clear(BackgroundColor); //给背景添加随机生成的燥点 if (this.Chaos) { Pen pen = new Pen(ChaosColor, 0); int c = Length * 10; for (int i = 0; i < c; i++) { int x = rnd.Next(image.Width); int y = rnd.Next(image.Height); g.DrawRectangle(pen, x, y, 1, 1); } } int left = 0, top = 0, top1 = 1, top2 = 1; int n1 = (imageHeight - FontSize - Padding * 2); int n2 = n1 / 4; top1 = n2; top2 = n2 * 2; Font f; Brush b; int cindex, findex; //随机字体和颜色的验证码字符 for (int i = 0; i < code.Length; i++) { cindex = rnd.Next(Colors.Length - 1); findex = rnd.Next(Fonts.Length - 1); f = new System.Drawing.Font(Fonts[findex], fSize, System.Drawing.FontStyle.Bold); b = new System.Drawing.SolidBrush(Colors[cindex]); if (i % 2 == 1) { top = top2; } else { top = top1; } left = i * fWidth; g.DrawString(code.Substring(i, 1), f, b, left, top); } //画一个边框 边框颜色为Color.Gainsboro g.DrawRectangle(new Pen(Color.Gainsboro, 0), 0, 0, image.Width - 1, image.Height - 1); g.Dispose(); //产生波形(Add By 51aspx.com) image = TwistImage(image, true, 8, 4); return image; } /// <summary> /// 生成随机字符码 /// </summary> /// <param name="codeLen">字符串长度</param> /// <param name="zhCharsCount">中文字符数</param> /// <returns></returns> public string CreateVerifyCode(int codeLen, int zhCharsCount) { char[] chs = new char[codeLen]; int index; for (int i = 0; i < zhCharsCount; i++) { index = rnd.Next(0, codeLen); if (chs[index] == ' ') chs[index] = CreateZhChar(); else --i; } for (int i = 0; i < codeLen; i++) { if (chs[i] == ' ') chs[i] = CreateEnOrNumChar(); } return new string(chs, 0, chs.Length); } /// <summary> /// 生成默认长度5的随机字符码 /// </summary> /// <returns></returns> public string CreateVerifyCode() { return CreateVerifyCode(Length, 0); } /// <summary> /// 生成英文或数字字符 /// </summary> /// <returns></returns> protected char CreateEnOrNumChar() { return EnglishOrNumChars[rnd.Next(0, EnglishOrNumChars.Length)]; } /// <summary> /// 生成汉字字符 /// </summary> /// <returns></returns> protected char CreateZhChar() { //若提供了汉字集,查询汉字集选取汉字 if (ChineseChars.Length > 0) { return ChineseChars[rnd.Next(0, ChineseChars.Length)]; } //若没有提供汉字集,则根据《GB2312简体中文编码表》编码规则构造汉字 else { byte[] bytes = new byte[2]; //第一个字节值在0xb0, 0xf7之间 bytes[0] = (byte)rnd.Next(0xb0, 0xf8); //第二个字节值在0xa1, 0xfe之间 bytes[1] = (byte)rnd.Next(0xa1, 0xff); //根据汉字编码的字节数组解码出中文汉字 string str1 = Encoding.GetEncoding("gb2312").GetString(bytes); return str1[0]; } } }
这里面大量使用了51aspx.com的代码,在此表示感谢。这里的主要改进在于支持生成中英文混合的验证码。中文的生成有两种方式,一是根据《GB2312简体中文编码表》编码规则构造汉字,二是从一个选定的中文字符集合中随即选取汉字。实现很简单,参考函数protected char CreateZhChar(),在此不赘述。
最后说一下验证码的使用,下面是一个例子:
<img src="VerifyCode.aspx" id="valiCode" alt="验证码" />
这里有个小技巧,就是在刷新验证码的使用,验证码的URL后面用了随机参数以欺骗浏览器重新请求。