Default.aspx
<head id="Head1" runat="server">
<title>Untitled Page</title>
<script type="text/javascript">function show(im)
{
im.src="Default2.aspx?"+new Date;//注意这里的new Date一定要加上，否则只会生成一次验证码
}
</script>
</head>
<div>
<img src="Default2.aspx" onclick ="show(this)" />
</div>
Default2.aspx.cs
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.Drawing;
using System.Drawing.Drawing2D;
public partial class Default2 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
CreateCheckCodeImage(GenerateCheckCode());
}
/// <summary>
/// 生成随机校验码字符串
/// </summary>
/// <returns>生成的随机校验码字符串</returns>
public string GenerateCheckCode()
{
int number;
string strCode = string.Empty;
//随机数种子
Random radom = new Random();
for (int i = 0; i < 4; i++)
{
//随机的整数
number = radom.Next();
//字符从０－９，Ａ－Ｚ中随机产生，对应的ＡＳＣＩＩ码分别为48-57,65,90
number = number % 36;
if (number < 10)
{
number += 48;
}
else
{
number += 55;
}
strCode += ((char)number).ToString();
}
//在Cookie中保存校验码或Session中
Response.Cookies.Add(new HttpCookie("CheckCode", strCode));
return strCode;
}
/// <summary>
/// 根据校验码输出图片
/// </summary>
/// <param name="checkCode">产生的随机校验码</param>
public void CreateCheckCodeImage(string checkCode)
{
//若校验码为空，则直接返回
if (checkCode == null || checkCode.Trim() == string.Empty)
{
return;
}
//根据校验码的长度确定输出图片的长度
System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling(decimal.Parse((checkCode.Length * 15) + "")), 20);
//创建ＧＲＡＰＨＩＣＳ对象
System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(image);
try
{
//生成随机数种子
Random random = new Random();
//清空图片背景色
g.Clear(System.Drawing.Color.White);
//画图片的背景噪音线１０条
for (int i = 0; i < 10; i++)
{
//噪音线起点坐标（x1,y1），终点坐标（x2,y2）
int x1 = random.Next(image.Width);
int x2 = random.Next(image.Width);
int y1 = random.Next(image.Height);
int y2 = random.Next(image.Height);
//用银色画出噪音线
g.DrawLine(new System.Drawing.Pen(System.Drawing.Color.Silver), x1, y1, x2, y2);
}
//输出图片中校验码的字体：１２号Arial,粗斜体
System.Drawing.Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
//线形渐变画刷
System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new System.Drawing.Rectangle(0, 0, image.Width, image.Height), System.Drawing.Color.Blue, System.Drawing.Color.Purple, 1.2f, true);
g.DrawString(checkCode, font, brush, 2, 3);
//画图片的前景噪音点５０个
for (int i = 0; i < 50; i++)
{
int x = random.Next(image.Width);
int y = random.Next(image.Height);
image.SetPixel(x, y, System.Drawing.Color.FromArgb(random.Next()));
}
//画图片的边框线
g.DrawRectangle(new System.Drawing.Pen(System.Drawing.Color.SaddleBrown), 0, 0, image.Width - 1, image.Height - 1);
//创建内存流用于输出图片
using (System.IO.MemoryStream ms = new System.IO.MemoryStream())
{
//图片格式指定为ＰＮＧ
image.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
//清除缓冲区流中的所有输出
Response.ClearContent();
//输出流的ＨＴＴＰＭＩＭＥ类型设置为＂image/Png＂
Response.ContentType = "image/Png";
//输出图片的二进制流
Response.BinaryWrite(ms.ToArray());
}
}
finally
{
//释放 Ｂitmap 对象和 Ｇraphics 对象
g.Dispose();
image.Dispose();
}
}
}