绘制汉字验证码

1、check.aspx.cs页面：

protected void Page_Load(object sender, EventArgs e)
{
GraphicsImage(4);
}
private object[] CreateString(int strlength)
{
//定义一个数组存储汉子编码的组成元素
string[] str = new string[16] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };
Random rd = 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 = rd.Next(11, 14);
string str1 = str[ran1].Trim();
//获取区位码第二位并防止数据重复
rd=new Random(ran1*unchecked((int)DateTime.Now.Ticks)+i);
int ran2;
if (ran1 == 13)
{
ran2 = rd.Next(0, 7);
}
else
{
ran2=rd.Next(0,16);
}
string str2 = str[ran2].Trim();
int ran3 = rd.Next(10, 16);
string str3 = str[ran3].Trim();//获取区位码第三位
rd=new Random(ran3*unchecked((int)DateTime.Now.Ticks)+i);
int ran4;
if (ran3 == 10)
{
ran4 = rd.Next(1, 16);
}
else if (ran3 == 15)
{
ran4 = rd.Next(0, 15);
}
else
{
ran4 = rd.Next(0, 16);
}
string str4 = str[ran4].Trim();//获取区位码第四位
byte byte1 = Convert.ToByte(str1 + str2, 16);//定义字节变量存储产生的随机汉字区位码
byte byte2 = Convert.ToByte(str3 + str4, 16);
byte[] stradd = new byte[] {byte1,byte2 };
bytes.SetValue(stradd, i);//将产生的汉字字节放入数组
}
return bytes;
}
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("check",str));
HttpContext.Current.Session["check"] = str;
return str;
}
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);
}

}

2、Default.aspx页面

<asp:Image ID="Image1" src="check.aspx" runat="server" Height="21px" Width="85px" onclick="this.src='check.aspx?aaa='+new Date()"/></td>

 

string check = Session["check"].ToString();
if (check == TextBox3.Text.Trim())
{
Response.Write("<script>alert('验证码正确！')</script>");
}
else
{
Response.Write("<script>alert('验证码错误！')</script>");
}