12306奇葩验证码引发思考之C#实现验证码程序

近日铁路订票网“12306”又出现多道另类考题，竟要订票者在8个图案中“点击图中所有美男子”、“请点击下图中所有的非智能眼镜”、“请点击下图中所有的博斯普鲁斯海峡”，网友吐槽：比高考题还难，到底是什么样子的，先跟大家分享一下几个例子：

哈哈，是有点奇葩的验证码，怪不得有人会说“妈妈我已经找不到回家”，这让分秒必争的春运网上抢票者瞬间傻眼，九成网友已经被打败……

正巧小编最近也在研究验证码，参考了许多网上案例，整理了一篇文章特分享给大家。

验证码的一般编写思路为：
       1.定义验证码字符长度;
       2.根据长度随机生成验证码字符串;
       3.将验证码字符串转换成图片形式，并在图片中生成随机噪声点和声线（对验证码进行模糊识别处理）;
       4.显示结果。

 ///
 /// 生成随机验证码
 ///
 /// 验证码长度
 ///
 public string CreateIdentifyingCode(int CodeLen)
 {
 if (CodeLen < 1)
  return String.Empty;
 int num;
 string checkcode = String.Empty;
 Random random = new Random();
 for (int index = 0; index < CodeLen; index++)
 {
  num = random.Next();
  if (num % 2 == 0)
  checkcode += (char)('0' + (char)(num % 10));
  else
  checkcode += (char)('A' + (char)(num % 26));
 }
 return checkcode;
 }
-------------------------------------------------------------------------------------------------
 ///
 /// 生成验证码图片
 ///
 ///
 /// 
 private void CreateCheckCodeImage(string checkcode)
 {
  if (checkcode == null || checkcode.Trim() == String.Empty)
  return;
  //创建图片大小
  System.Drawing.Bitmap image = new  System.Drawing.Bitmap((int)Math.Ceiling(checkcode.Length*12.5),22);
  //创建画板
  Graphics graphic = Graphics.FromImage(image);
 
  try
  {
  Random random = new Random();
  graphic.Clear(Color.White);
  int x1 = 0, y1 = 0, x2 = 0, y2 = 0;
  //画图片背景噪声线
  for (int index = 0; index < 25; index++)
  {
   x1 = random.Next(image.Width);
   y1 = random.Next(image.Height);
   x2 = random.Next(image.Width);
   y2 = random.Next(image.Height);
   graphic.DrawLine(new Pen(Color.Silver),x1,y1,x2,y2);
  }
  Font font = new System.Drawing.Font("Helvetica", 12, (FontStyle.Bold |FontStyle.Italic));
  LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height),Color.Blue,Color.DarkBlue,1.2f,true);
  graphic.DrawString(checkcode,font,brush,2,2);
 
  int x = 0;
  int y = 0;
  // 画图片的前景噪声点
  for (int index = 0; index < 100; index++)
  {
   x = random.Next(image.Width);
   y = random.Next(image.Height);
   image.SetPixel(x,y,Color.FromArgb(random.Next()));
  }
  //画图片的边框线
  graphic.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
  //网页响应
  System.IO.MemoryStream ms = new System.IO.MemoryStream();
  image.Save(ms,System.Drawing.Imaging.ImageFormat.Gif);
  Response.ClearContent();
  Response.ContentType = "image/Gif";
  Response.BinaryWrite(ms.ToArray());
  }
  finally
  {
  graphic.Dispose();
  image.Dispose();
  }
 }

以上所生成的为简单的验证码。接下来我从其他的博客中学习了其他形式的效果。

/* 图片画线特殊效果：贝塞尔曲线 */
  Graphics graph = Graphics.FromImage(image);
  graph.Clear(Color.WhiteSmoke);
  Point[] myArray ={
     new Point(random.Next(150),random.Next(50)),
     new Point(random.Next(150),random.Next(50)),
     new Point(random.Next(150),random.Next(50)),
     new Point(random.Next(150),random.Next(50)),
     new Point(random.Next(150),random.Next(50)),
     new Point(random.Next(150),random.Next(50)),
     new Point(random.Next(150),random.Next(50)),
     new Point(random.Next(150),random.Next(50)),
     new Point(random.Next(150),random.Next(50)),
     new Point(random.Next(150),random.Next(50))
    };
  Pen myPen = new Pen(Color.Blue, 1);
  GraphicsPath myPath = new GraphicsPath();
  myPath.AddBeziers(myArray);
  graph.DrawPath(myPen, myPath);

验证码字符颜色变换效果：实现该效果，我们首先来定义一个颜色集合，然后通过for循环使其随机改变字体颜色则可。

 #region 定义颜色数组
 Color[] colors = { Color.Blue, Color.Green, Color.Red, Color.Gold, Color.Black, Color.Chocolate, Color.Orange, Color.Purple };
 public Color[] Colors
 {
  get { return colors; }
  set { colors = value; }
 }
 #endregion
 Brush brush;
 int colornum;
 for(int i=0; i
 {
  colornum = random.Next(Colors.Length - 1);
  brush = new System.Drawing.SolidBrush(Colors[cindex]);
 
  //利用DrawString函数进行颜色填充就可以了。
 }

 同样的原理我们也可以定义一个字体的数组来进行验证码字体切换。代码和颜色的类似，这里就不加以累赘。
接下来看看如何使得验证码的字体进行扭曲。

private const double PI = 3.1415926535897932384626433832795;
 private const double PI2 = 6.283185307179586476925286766559;
 ///
 /// 波形滤镜效果函数
 ///
 ///
 ///
 ///
 ///
 ///
 public System.Drawing.Bitmap TwistImage(Bitmap srcbmp, double dmultvalue, double dphase)
 {
  System.Drawing.Bitmap destbmp = new Bitmap(srcbmp.Width,srcbmp.Height);
  System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(destbmp);
  //填充背景图为白色
  graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), 0, 0, destbmp.Width, destbmp.Height);
  graph.Dispose();
  double dbaselen = (double)destbmp.Width;
  for (int i = 0; i < destbmp.Width; i++)
  {
  for (int j = 0; j < destbmp.Height; j++)
  {
   double dx = 0;
   dx = (PI2 * (double)j) / dbaselen;
   dx += dphase;
 
   double dy = Math.Sin(dx);
 
   int noldx = 0, noldy = 0;
   noldx = i + (int)(dy * dmultvalue);
   noldy = 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;
 }

上面代码是参考了这段代码进行的学习<C#.net 好用的验证码代码 汉字-变色-扭曲-波动 >，代码如下

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Drawing;
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;

public partial class study_CheckCode2 : System.Web.UI.Page
{
 protected void Page_Load(object sender, EventArgs e)
 {
 string code = CreateVerifyCode();  //取随机码
 CreateImageOnPage(code, this.Context); // 输出图片
 Response.Cookies.Add(new HttpCookie("CheckCode", code.ToUpper()));// 使用Cookies取验证码的值
 }

 #region 验证码长度(默认4个验证码的长度)
 int length = 4;
 public int Length
 {
 get { return length; }
 set { length = value; }
 }
 #endregion

 #region 验证码字体大小(为了显示扭曲效果，默认40像素，可以自行修改)
 int fontSize = 40;
 public int FontSize
 {
 get { return fontSize; }
 set { fontSize = value; }
 }
 #endregion

 #region 边框补(默认1像素)
 int padding = 2;
 public int Padding
 {
 get { return padding; }
 set { padding = value; }
 }
 #endregion

 #region 是否输出燥点(默认不输出)
 bool chaos = tr