本文实例讲述了ASP.NET生成图形验证码的方法。分享给大家供大家参考,具体如下:
通常生成一个图形验证码主要 有3个步骤:
(1)随机产生一个长度为N的随机字符串,N的值可由开发可由开发人员自行设置。该字符串可以包含数字、字母等。
(2)将随机生成的字符串创建成图片,并显示。
(3)保存验证码。
新建一个页面为default.aspx, 放置一个TextBox控件和一个Image控件,TextBox控件用于输入生成的字符串,Image控件用于显示字符串,它的图片就为生成的图形验证码imageUrl=“/default.aspx”;
default.aspx页面的源代码为:
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<form id= "form1" runat= "server" >
<div>
<asp:TextBox ID= "TextBox1" runat= "server" ></asp:TextBox>
<asp:Image ID= "Image1" imageUrl=“/ default .aspx” runat= "server" />
</div>
</form>
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图形验证码的代码为:
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using System;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Drawing;
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load( object sender, EventArgs e)
{
if (!IsPostBack)
{
string validateNum = CreateRandomNum(4);
CreateImage(validateNum);
Session[ "ValidateNum" ] = validateNum;
}
}
//生产随机数
private string CreateRandomNum( int NumCount)
{
string allChar = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,O,P,Q,R,S,T,U,W,X,Y,Z,a,b,c,d,e,f,g,h,i,j,k,m,n,o,p,q,s,t,u,w,x,y,z" ;
string [] allCharArray = allChar.Split( ',' ); //拆分成数组
string randomNum = "" ;
int temp = -1; //记录上次随机数的数值,尽量避免产生几个相同的随机数
Random rand = new Random();
for ( int i = 0; i < NumCount; i++)
{
if (temp != -1)
{
rand = new Random(i*temp*(( int )DateTime.Now.Ticks));
}
int t = rand.Next(35);
if (temp == t)
{
return CreateRandomNum(NumCount);
}
temp = t;
randomNum += allCharArray[t];
}
return randomNum;
}
//生产图片
private void CreateImage( string validateNum)
{
if (validateNum == null || validateNum.Trim() == string .Empty)
return ;
//生成BitMap图像
System.Drawing.Bitmap image = new System.Drawing.Bitmap(validateNum.Length*12+12,22);
Graphics g = Graphics.FromImage(image);
try
{
//生成随机生成器
Random random = new Random();
//清空图片背景
g.Clear(Color.White);
//画图片的背景噪音线
for ( int i = 0; i < 25; 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.Silver),x1,x2,y1,y2);
}
Font font = new System.Drawing.Font( "Arial" ,12,(System.Drawing.FontStyle.Bold|System.Drawing.FontStyle.Italic));
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(validateNum,font,brush ,2,2);
//画图片的前景噪音点
for ( int i=0;i<100;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();
//将图像保存到指定流
image.Save(ms,System.Drawing.Imaging.ImageFormat.Gif);
Response.ClearContent();
Response.ContentType= "image/Gif" ;
Response.BinaryWrite(ms.ToArray());
}
finally
{
g.Dispose();
image.Dispose();
}
}
}
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希望本文所述对大家asp.net程序设计有所帮助。