汉字验证码

有时在注册论坛会员时，网页中的验证码是以汉字形式出现的。汉字验证码技术比字母和数字混合验证码技术更先进。通过汉字验证码，可以有效地防止非法用户灌水。

本实例中主要通过生成的汉字区位码，将其转换成汉字。

区位码是汉字一一对应的编码，用4位数字表示，前两位从01到94称为区码，后两位从01到94称为位码，一个汉字的前一半是ASC II码位“160+区码”的字符，后一半是ASC II码“160+位码”的字符。

今天把主要代码给贴出来供需要的朋友参考下：

在页面加载时调用相应的方法就可以了：

protected void Page_Load(object sender, EventArgs e)
{
GraphicsImage(4); //调用方法生成四位汉字验证码
}

private void GraphicsImage(int length)
{
System.Drawing.Bitmap image =
new System.Drawing.Bitmap((int)Math.Ceiling((GetString(length).Length * 22.5)), 22);
Graphics g = Graphics.FromImage(image); //创建画布
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
for (int i = 0; i < 1; 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(Color.Black), x1, y1, x2, y2);
}
Font font = new System.Drawing.Font("Couriew New", 12, System.Drawing.FontStyle.Bold);
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.DrawString(GetString(length), font, brush, 2, 2);
//画图片的前景噪音点
for (int i = 0; i < 50; i++)
{
int x = random.Next(image.Width);
int y = random.Next(image.Height);

image.SetPixel(x, y, Color.FromArgb(random.Next()));
}
//画图片的边框线
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);
Response.ClearContent();
Response.ContentType = "image/Gif";
Response.BinaryWrite(ms.ToArray());
}
catch (Exception ms)
{
Response.Write(ms.Message);
}
}private string GetString(int length)
{
Encoding gb = Encoding.GetEncoding("gb2312");
object[] bytes = CreateString(length);
//根据汉字字节解码出中文汉字
string str1 = gb.GetString((byte[])Convert.ChangeType(bytes[0], typeof(byte[])));
string str2 = gb.GetString((byte[])Convert.ChangeType(bytes[1], typeof(byte[])));
string str3 = gb.GetString((byte[])Convert.ChangeType(bytes[2], typeof(byte[])));
string str4 = gb.GetString((byte[])Convert.ChangeType(bytes[3], typeof(byte[])));
string str = str1 + str2 + str3 + str4;
Response.Cookies.Add(new HttpCookie("CheckCode", str));
return str;
}private object[] CreateString(int strlength)
{
//定义一个数组存储汉字编码的组成元素
string[] str = new string[16]
{ "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };
Random ran = new Random(); //定义一个随机数对象
object[] bytes = new object[strlength];
for (int i = 0; i < strlength; i++)
{
//获取区位码第一位
int ran1 = ran.Next(11, 14);
string str1 = str[ran1].Trim();
//获取区位码第二位并防止数据重复
ran = new Random(ran1 * unchecked((int)DateTime.Now.Ticks) + i);
int ran2;
if (ran1 == 13)
{
ran2 = ran.Next(0, 7);
}
else
{
ran2 = ran.Next(0, 16);
}
string str2 = str[ran2].Trim();
//获取区位码第三位
ran = new Random(ran2 * unchecked((int)DateTime.Now.Ticks) + i);
int ran3 = ran.Next(10, 16);
string str3 = str[ran3].Trim();
//获取区位码第四位
ran = new Random(ran3 * unchecked((int)DateTime.Now.Ticks) + i);
int ran4;
if (ran3 == 10)
{
ran4 = ran.Next(1, 16);
}
else if (ran3 == 15)
{
ran4 = ran.Next(0, 15);
}
else
{
ran4 = ran.Next(0, 16);
}
string str4 = str[ran4].Trim();
//定义字节变量存储产生的随机汉字区位码
byte byte1 = Convert.ToByte(str1 + str2, 16);
byte byte2 = Convert.ToByte(str3 + str4, 16);
byte[] stradd = new byte[] { byte1, byte2 };
//将产生的汉字字节放入数组
bytes.SetValue(stradd, i);
}
return bytes;
}

原帖地址：http://www.cnblogs.com/wangsaiming/archive/2011/06/27/2091256.html