中文验证码

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

public partial class Member_checkcode : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
//调用函数产生4个随机中文汉字编码
string randomcode = CreateRegionCode(4);
Session["ValidNum"] = randomcode;
this.CreateImage(randomcode);
}
/**/
/// <summary>
/// 中文
/// </summary>
/// <param name="strlength"></param>
/// <returns></returns>
public string CreateRegionCode(int strlength)
{
//定义一个字符串数组储存汉字编码的组成元素
string[] rBase = new String[16] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };
Random rnd = new Random();

//定义一个object数组用来
object[] bytes = new object[strlength];

/**/
/**/
/**/
/*每循环一次产生一个含两个元素的十六进制字节数组，并将其放入bject数组中
每个汉字有四个区位码组成
区位码第1位和区位码第2位作为字节数组第一个元素
区位码第3位和区位码第4位作为字节数组第二个元素
*/
for (int i = 0; i < strlength; i++)
{
//区位码第1位
int r1 = rnd.Next(11, 14);
string str_r1 = rBase[r1].Trim();

//区位码第2位
rnd = new Random(r1 * unchecked((int)DateTime.Now.Ticks) + i);//更换随机数发生器的种子避免产生重复值
int r2;
if (r1 == 13)
r2 = rnd.Next(0, 7);
else
r2 = rnd.Next(0, 16);
string str_r2 = rBase[r2].Trim();

//区位码第3位
rnd = new Random(r2 * unchecked((int)DateTime.Now.Ticks) + i);
int r3 = rnd.Next(10, 16);
string str_r3 = rBase[r3].Trim();

//区位码第4位
rnd = new Random(r3 * unchecked((int)DateTime.Now.Ticks) + i);
int r4;
if (r3 == 10)
r4 = rnd.Next(1, 16);
else if (r3 == 15)
r4 = rnd.Next(0, 15);
else
r4 = rnd.Next(0, 16);
string str_r4 = rBase[r4].Trim();

//定义两个字节变量存储产生的随机汉字区位码
byte byte1 = Convert.ToByte(str_r1 + str_r2, 16);
byte byte2 = Convert.ToByte(str_r3 + str_r4, 16);
//将两个字节变量存储在字节数组中
byte[] str_r = new byte[] { byte1, byte2 };

//将产生的一个汉字的字节数组放入object数组中
bytes.SetValue(str_r, i);

}

//获取GB2312编码页（表）
Encoding gb = Encoding.GetEncoding("gb2312");

//根据汉字编码的字节数组解码出中文汉字
string strResult = "";
for (int i = 0; i < strlength; i++)
{
strResult += gb.GetString((byte[])Convert.ChangeType(bytes[i], typeof(byte[])));
}

return strResult;
}

/**/
/// <summary>
/// 创建随机码图片
/// </summary>
/// <param name="randomcode">随机码</param>
private void CreateImage(string randomcode)
{
int randAngle = 30; //随机转动角度
int mapwidth = (int)(randomcode.Length * 28);
Bitmap map = new Bitmap(mapwidth, 28);//创建图片背景
Graphics graph = Graphics.FromImage(map);
graph.Clear(Color.AliceBlue);//清除画面，填充背景
graph.DrawRectangle(new Pen(Color.Black, 0), 0, 0, map.Width - 1, map.Height - 1);//画一个边框
//graph.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;//模式

Random rand = new Random();
//背景噪点生成
Pen blackPen = new Pen(Color.LightGray, 0);
for (int i = 0; i < 50; i++)
{
int x = rand.Next(0, map.Width);
int y = rand.Next(0, map.Height);
graph.DrawRectangle(blackPen, x, y, 1, 1);
}

//验证码旋转，防止机器识别
char[] chars = randomcode.ToCharArray();//拆散字符串成单字符数组
//文字距中
StringFormat format = new StringFormat(StringFormatFlags.NoClip);
format.Alignment = StringAlignment.Center;
format.LineAlignment = StringAlignment.Center;
//定义颜色
Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };
//定义字体
string[] font = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };
for (int i = 0; i < chars.Length; i++)
{
int cindex = rand.Next(7);
int findex = rand.Next(5);
Font f = new System.Drawing.Font(font[findex], 13, System.Drawing.FontStyle.Bold);//字体样式(参数2为字体大小)
Brush b = new System.Drawing.SolidBrush(c[cindex]);
Point dot = new Point(22, 16);
//graph.DrawString(dot.X.ToString(),fontstyle,new SolidBrush(Color.Black),10,150);//测试X坐标显示间距的
float angle = rand.Next(-randAngle, randAngle);//转动的度数
graph.TranslateTransform(dot.X, dot.Y);//移动光标到指定位置
graph.RotateTransform(angle);
graph.DrawString(chars[i].ToString(), f, b, 1, 1, format);
//graph.DrawString(chars[i].ToString(),fontstyle,new SolidBrush(Color.Blue),1,1,format);
graph.RotateTransform(-angle);//转回去
graph.TranslateTransform(2, -dot.Y);//移动光标到指定位置
}
//graph.DrawString(randomcode,fontstyle,new SolidBrush(Color.Blue),2,2); //标准随机码

//生成图片
System.IO.MemoryStream ms = new System.IO.MemoryStream();
map.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
Response.ClearContent();
Response.ContentType = "image/gif";
Response.BinaryWrite(ms.ToArray());
graph.Dispose();
map.Dispose();
}

}

使用验证码的前台

<tr><td align="right"> 验&nbsp;证&nbsp;码&nbsp;<span class="red">*</span></td><td> <label>
<input type="text" name="txtValidNum" id="txtValidNum" class="int6" />
</label> <img alt="" id="imgsrc" src="checkcode.aspx" onclick="imgchange()" style="cursor: pointer;" />
<label onclick="imgchange()" style="cursor: pointer;">
图片验证码看不清，换一张</label></td></tr>

使用的js判断

function imgchange()
{
document.getElementById("imgsrc").src="checkcode.aspx?"+new Date;
}

在使用到验证码的地方后台进行判断

if (Request["txtValidNum"].Trim() != Session["ValidNum"].ToString())
{
__GotoWebMsg("验证码错误！");
return;
}