验证码技术是网站开发过程中比较重要的技术,可以防止非法人员利用注册机或者登陆工具来攻击我们的网站。下面是效果图:
具体实现方法如下:
1、主要思路是:引用Using System.Drawing命名空间,利用Graphics的FromImage方法创建一个画布,同时设置画布的宽和高,然后通过Graphics类 的DrawString方法随机生成的字符串绘制到画布中,绘制验证码的同时,在画布中利用SetPixel方法绘制一些色点,从而防止非法人员利用机器 人来进行登陆。当我们绘制验证码完毕后,在需要验证码的页面中利用Image空间将其显示出来,Image控件显示验证码的HTML源码设置如下:
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< asp:Image ID = "Image1" runat = "server" ImageUrl = "~/ValidateNum.aspx" />
< asp:LinkButton ID = "LinkButton1" runat = "server" style = "font-size: small; " >看不清,换一张</ asp:LinkButton >
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2、这里所用到的ValidateNum.aspx页面代码如下:
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using System;
using System.Collections;
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 ValidateNum : System.Web.UI.Page
{
protected void Page_Load( object sender, EventArgs e)
{
if (!IsPostBack)
{
string validateNum = CreateRandomNum(4); //成生4位随机字符串
Session[ "ValidateNum" ] = validateNum; //保存验证码
}
}
//生成随机字符串
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,L,M,N,O,P,Q,R,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;
}
//生成图片
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 + 10, 22);
Graphics g = Graphics.FromImage(image);
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 < 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, y1, x2, 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();
//将图像保存到指定的流
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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以上就是关于asp.net生成图形验证码的相关资料,希望对大家的学习有所帮助。