一、验证码简介
验证码功能一般是用于防止批量注册的,不少网站为了防止用户利用机器人自动注册、登录、灌水,都采用了验证码技术。所谓验证码,就是将一串随机产生的数字或字母或符号或文字,生成一幅图片, 图片里加上一些干扰象素(防止OCR),由用户肉眼识别其中的验证码信息,输入表单提交网站验证,验证成功后才能使用某项功能。
常见的验证码有如下几种:
1、纯数字验证码,一般为四位随机数字;
2、数字+字母验证码,一般从数字(0~9)和字母(A~Z和a~z)中随机抽出几个字符组成;
3、汉字验证码,相对而言,这种验证码比较少见一点,实现起来也相对复杂一些,但在不少网站中还是可以看到的;
二、验证码的实现
1、纯数字验证码的实现
纯数字验证码的实现相对比较简单,可通过以下两种方法来实现
(1)使用随机数方式,代码如下:
private
String GetRandomint(
int
codeCount)
{
Random random
=
new
Random();
string
min
=
""
;
string
max
=
""
;
for
(
int
i
=
0
; i
<
codeCount; i
++
)
{
min
+=
"
1
"
;
max
+=
"
9
"
;
}
return
(random.Next(Convert.ToInt32(min),Convert.ToInt32(max)).ToString());
}
(2)使用随机组合方式,代码如下:
private
string
CreateRandomCode(
int
codeCount)
{
string
allChar
=
"
0,1,2,3,4,5,6,7,8,9
"
;
string
[] allCharArray
=
allChar.Split(
'
,
'
);
string
randomCode
=
""
;
int
temp
=
-
1
;
Random rand
=
new
Random();
for
(
int
i
=
0
; i
<
codeCount; i
++
)
{
if
(temp
!=
-
1
)
{
rand
=
new
Random(i
*
temp
*
((
int
)DateTime.Now.Ticks));
}
int
t
=
rand.Next(
9
);
if
(temp
==
t)
{
return
CreateRandomCode(codeCount);
}
temp
=
t;
randomCode
+=
allCharArray[t];
}
return
randomCode;
}
2、数字+字母验证码的实现,代码如下:
private
string
CreateRandomCode(
int
codeCount)
{
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,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z
"
;
string
[] allCharArray
=
allChar.Split(
'
,
'
);
string
randomCode
=
""
;
int
temp
=
-
1
;
Random rand
=
new
Random();
for
(
int
i
=
0
; i
<
codeCount; i
++
)
{
if
(temp
!=
-
1
)
{
rand
=
new
Random(i
*
temp
*
((
int
)DateTime.Now.Ticks));
}
int
t
=
rand.Next(
61
);
if
(temp
==
t)
{
return
CreateRandomCode(codeCount);
}
temp
=
t;
randomCode
+=
allCharArray[t];
}
return
randomCode;
}
3、汉字验证码的实现,代码如下:
/**/
/*
此函数在汉字编码范围内随机创建含两个元素的十六进制字节数组,每个字节数组代表一个汉字,并将
四个字节数组存储在object数组中。
参数:strlength,代表需要产生的汉字个数
*/
public
static
object
[] CreateRegionCode(
int
strlength)
{
//
定义一个字符串数组储存汉字编码的组成元素
string
[] rBase
=
new
String[
16
] {
"
0
"
,
"
1
"
,
"
2
"
,
"
3
"
,
"
4
"
,
"
5
"
,
"
6
"
,
"
7
"
,
"
8
"
,
"
9
"
,
"
a
"
,
"
b
"
,
"
c
"
,
"
d
"
,
"
e
"
,
"
f
"
};
Random rnd
=
new
Random();
//
定义一个object数组用来
object
[] bytes
=
new
object
[strlength];
/**/
/*
每循环一次产生一个含两个元素的十六进制字节数组,并将其放入bject数组中
每个汉字有四个区位码组成
区位码第1位和区位码第2位作为字节数组第一个元素
区位码第3位和区位码第4位作为字节数组第二个元素
*/
for
(
int
i
=
0
; i
<
strlength; i
++
)
{
//
区位码第1位
int
r1
=
rnd.Next(
11
,
14
);
string
str_r1
=
rBase[r1].Trim();
//
区位码第2位
rnd
=
new
Random(r1
*
unchecked
((
int
)DateTime.Now.Ticks)
+
i);
//
更换随机数发生器的种子避免产生重复值
int
r2;
if
(r1
==
13
)
{
r2
=
rnd.Next(
0
,
7
);
}
else
{
r2
=
rnd.Next(
0
,
16
);
}
string
str_r2
=
rBase[r2].Trim();
//
区位码第3位
rnd
=
new
Random(r2
*
unchecked
((
int
)DateTime.Now.Ticks)
+
i);
int
r3
=
rnd.Next(
10
,
16
);
string
str_r3
=
rBase[r3].Trim();
//
区位码第4位
rnd
=
new
Random(r3
*
unchecked
((
int
)DateTime.Now.Ticks)
+
i);
int
r4;
if
(r3
==
10
)
{
r4
=
rnd.Next(
1
,
16
);
}
else
if
(r3
==
15
)
{
r4
=
rnd.Next(
0
,
15
);
}
else
{
r4
=
rnd.Next(
0
,
16
);
}
string
str_r4
=
rBase[r4].Trim();
//
定义两个字节变量存储产生的随机汉字区位码
byte
byte1
=
Convert.ToByte(str_r1
+
str_r2,
16
);
byte
byte2
=
Convert.ToByte(str_r3
+
str_r4,
16
);
//
将两个字节变量存储在字节数组中
byte
[] str_r
=
new
byte
[] { byte1, byte2 };
//
将产生的一个汉字的字节数组放入object数组中
bytes.SetValue(str_r, i);
}
return
bytes;
}
三、具体实例
(实例1)
前台代码display.aspx
<body>
<form id="form1" runat="server">
<div>
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp:Image ID="Image1" runat="server" ImageUrl="png.aspx" /><br />
<br />
<asp:Button ID="Button2" runat="server" OnClick="Button2_Click" Text="Button" />
<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
<asp:ListItem Value="3">默认</asp:ListItem>
<asp:ListItem Value="1">文字</asp:ListItem>
<asp:ListItem Value="2">数字</asp:ListItem>
<asp:ListItem Value="3">混合</asp:ListItem>
</asp:DropDownList></div>
</form>
</body>
后台代码display.cs
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
switch (DropDownList1.SelectedValue)
{
case "1":
Image1.ImageUrl = "png.aspx?aa=1";
break;
case "2":
Image1.ImageUrl = "png.aspx?aa=2";
break;
case "3":
Image1.ImageUrl = "png.aspx?aa=3";
break;
}
}
protected void Button2_Click(object sender, EventArgs e)
{
if (TextBox1.Text == Session["gif"].ToString())
Response.Write("OK,正确");
else
Response.Write("验证码不符合");
}
后台代码png.cs
public partial class png : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
switch (Request.QueryString["aa"])
{
case "1":
gif = stxt(10);
Session["gif"] = stxt(10);
break;
case "2":
gif = GetRandomint(4);
Session["gif"] = GetRandomint(4);
break;
case "3":
gif = CreateRandomCode(4);
Session["gif"] = CreateRandomCode(4);
break;
default:
gif = CreateRandomCode(4);
Session["gif"] = CreateRandomCode(4);
break;
}
CreateImage(Session["gif"].ToString());
}
private String GetRandomint(int codeCount)
{
Random random = new Random();
string min = "";
string max = "";
for (int i = 0; i < codeCount; i++)
{
min +="1";
max+="9";
}
return (random.Next(Convert.ToInt32(min),Convert.ToInt32(max)).ToString());
}
/**/
/*
此函数在汉字编码范围内随机创建含两个元素的十六进制字节数组,每个字节数组代表一个汉字,并将
四个字节数组存储在object数组中。
参数:strlength,代表需要产生的汉字个数
*/
public static object[] CreateRegionCode(int strlength)
{
//定义一个字符串数组储存汉字编码的组成元素
string[] rBase = new String[16] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };
Random rnd = new Random();
//定义一个object数组用来
object[] bytes = new object[strlength];
/**/
/*每循环一次产生一个含两个元素的十六进制字节数组,并将其放入bject数组中
每个汉字有四个区位码组成
区位码第1位和区位码第2位作为字节数组第一个元素
区位码第3位和区位码第4位作为字节数组第二个元素
*/
for (int i = 0; i < strlength; i++)
{
//区位码第1位
int r1 = rnd.Next(11, 14);
string str_r1 = rBase[r1].Trim();
//区位码第2位
rnd = new Random(r1 * unchecked((int)DateTime.Now.Ticks) + i);//更换随机数发生器的种子避免产生重复值
int r2;
if (r1 == 13)
{
r2 = rnd.Next(0, 7);
}
else
{
r2 = rnd.Next(0, 16);
}
string str_r2 = rBase[r2].Trim();
//区位码第3位
rnd = new Random(r2 * unchecked((int)DateTime.Now.Ticks) + i);
int r3 = rnd.Next(10, 16);
string str_r3 = rBase[r3].Trim();
//区位码第4位
rnd = new Random(r3 * unchecked((int)DateTime.Now.Ticks) + i);
int r4;
if (r3 == 10)
{
r4 = rnd.Next(1, 16);
}
else if (r3 == 15)
{
r4 = rnd.Next(0, 15);
}
else
{
r4 = rnd.Next(0, 16);
}
string str_r4 = rBase[r4].Trim();
//定义两个字节变量存储产生的随机汉字区位码
byte byte1 = Convert.ToByte(str_r1 + str_r2, 16);
byte byte2 = Convert.ToByte(str_r3 + str_r4, 16);
//将两个字节变量存储在字节数组中
byte[] str_r = new byte[] { byte1, byte2 };
//将产生的一个汉字的字节数组放入object数组中
bytes.SetValue(str_r, i);
}
return bytes;
}
private string stxt(int num)
{
Encoding gb = Encoding.GetEncoding("gb2312");
//调用函数产生10个随机中文汉字编码
object[] bytes = CreateRegionCode(num);
string strtxt = "";
//根据汉字编码的字节数组解码出中文汉字
for (int i = 0; i < num; i++)
{
strtxt += gb.GetString((byte[])Convert.ChangeType(bytes[i], typeof(byte[])));
}
return strtxt;
}
/// <summary>
/// 这个是使用字母,数字混合
/// </summary>
/// <param name="VcodeNum"></param>
/// <returns></returns>
private string CreateRandomCode(int codeCount)
{
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,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z";
string[] allCharArray = allChar.Split(',');
string randomCode = "";
int temp = -1;
Random rand = new Random();
for (int i = 0; i < codeCount; i++)
{
if (temp != -1)
{
rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
}
int t = rand.Next(61);
if (temp == t)
{
return CreateRandomCode(codeCount);
}
temp = t;
randomCode += allCharArray[t];
}
return randomCode;
}
private void CreateImage(string checkCode)
{
int iwidth = (int)(checkCode.Length * 20);
System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 25);
Graphics g = Graphics.FromImage(image);
Font f = new System.Drawing.Font("Arial", 10, System.Drawing.FontStyle.Bold);
Brush b = new System.Drawing.SolidBrush(Color.White);
//g.FillRectangle(new System.Drawing.SolidBrush(Color.Blue),0,0,image.Width, image.Height);
g.Clear(Color.Black);
g.DrawString(checkCode, f, b, 3, 3);
Pen blackPen = new Pen(Color.Black, 0);
Random rand = new Random();
//for (int i=0;i<5;i++)
//{
// int y = rand.Next(image.Height);
// g.DrawLine(blackPen,0,y,image.W
idth,y);
//}
System.IO.MemoryStream ms = new System.IO.MemoryStream();
image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
Response.ClearContent();
Response.ContentType = "image/Jpeg";
Response.BinaryWrite(ms.ToArray());
g.Dispose();
image.Dispose();
}
}
(实例2):20101018续加
调用页面前台代码
<
script
language
="Javascript"
>
function
Regist()
{
var
url
=
""
;
url
=
"
/GZPI/Service/Registry/ViewProtocol.aspx
"
;
window.open(url);
return
false
;
}
function
LoginClick()
{
if
(document.Login.UserName.value
==
""
)
{
alert(
"
用户名不能为空!
"
);
return
false
;
}
document.Login.submit();
document.Login.Password.value
=
""
;
return
false
;
}
function
f_refreshtype()
{
var
Image1
=
document.getElementById(
"
IMGCheckCode
"
);
if
(Image1
!=
null
)
{
Image1.src
=
Image1.src
+
"
?
"
;
}
}
</
script
>
<
TABLE
cellSpacing
="0"
cellPadding
="5"
width
="100%"
border
="0"
>
<
TR
>
<
TD
class
="fontblack"
align
="right"
width
="30%"
>
用 户 名:
</
TD
>
<
TD
vAlign
="bottom"
align
="left"
width
="62%"
><
input
id
="Text1"
style
="BORDER-RIGHT: #43a7e2 1px solid; BORDER-TOP: #43a7e2 1px solid; BACKGROUND: #fcfcfc; BORDER-LEFT: #43a7e2 1px solid; BORDER-BOTTOM: #43a7e2 1px solid"
size
="13"
name
="UserName"
width
="100px"
>
</
TD
>
</
TR
>
<
TR
>
<
TD
class
="fontblack"
align
="right"
height
="23"
>
密
码:
</
TD
>
<
TD
vAlign
="bottom"
align
="left"
height
="23"
><
input
id
="Password1"
style
="BORDER-RIGHT: #43a7e2 1px solid; BORDER-TOP: #43a7e2 1px solid; BACKGROUND: #fcfcfc; BORDER-LEFT: #43a7e2 1px solid; BORDER-BOTTOM: #43a7e2 1px solid"
type
="password"
size
="13"
name
="Password"
width
="100px"
>
</
TD
>
</
TR
>
<
TR
>
<
TD
class
="fontblack"
align
="right"
height
="23"
>
校
验 码:
</
TD
>
<
TD
valign
="top"
align
="left"
height
="23"
><
FONT
face
="宋体"
><
INPUT
id
="CheckCode"
style
="BORDER-RIGHT: #43a7e2 1px solid; BORDER-TOP: #43a7e2 1px solid; BACKGROUND: #fcfcfc; BORDER-LEFT: #43a7e2 1px solid; BORDER-BOTTOM: #43a7e2 1px solid"
width
="100px"
size
="13"
name
="CheckCode"
>
</
FONT
><
a
style
="CURSOR: hand"
onclick
="f_refreshtype()"
title
="看不清楚?点击获取新的校验码!"
border
="0"
><
IMG
id
="IMGCheckCode"
src
="../GenerateCheckCode.aspx"
></
a
>
</
TD
>
</
TR
>
<
TR
vAlign
="bottom"
align
="center"
>
<
TD
class
="dlbuttom"
colSpan
="2"
height
="23"
><
input
id
="Image1"
style
="CURSOR: hand"
onclick
="return LoginClick();"
tabIndex
="3"
type
="image"
height
="17"
width
="55"
src
="images/login.gif"
border
="0"
name
="OkButton"
>
<
input
type
="image"
onClick
="return Regist();"
border
='0'
src
='images/zuce.gif'
width
='55'
height
='17'
ID
="Image2"
NAME
="Image2"
>
</
TD
>
</
TR
>
</
TABLE
>
调用页面后台代码
private void OK_Click(object sender, System.EventArgs e)
{
if (!CheckCodeSame(CheckCode.Text.Trim()))
{
System.Web.HttpContext.Current.Response.Write("
<
Script
Language
='JavaScript'
>
window.alert(
'
校验码错误!请重新输入!
'
);window.close();
</
script
>
");
return;
}
int userType = 1;
try
{
userType = int.Parse(UserType.Text);
}
catch
{
}
GatewayManager gateway = new GatewayManager(corpCode.Text,collegeCode.Text,chargeCode.Text,userName.Text,password.Text,userType);
gateway.Login(this);
}
///
<
summary
>
/// 判断输入的校验码是否正确
///
</
summary
>
///
<
param
name
="checkCode"
></
param
>
///
<
returns
></
returns
>
public static bool CheckCodeSame(string checkCode)
{
bool bSame = false; ;
if (HttpContext.Current.Session["CheckCode"] != null)
{
if (checkCode.ToUpper() == HttpContext.Current.Session["CheckCode"].ToString().ToUpper())
{
bSame = true;
}
}
return bSame;
}
生成验证码前台文件
<
HTML
>
<
HEAD
>
<
title
>
GenerateCheckCode
</
title
>
<
meta
name
="GENERATOR"
Content
="Microsoft Visual Studio .NET 7.1"
>
<
meta
name
="CODE_LANGUAGE"
Content
="C#"
>
<
meta
name
="vs_defaultClientScript"
content
="JavaScript"
>
<
meta
name
="vs_targetSchema"
content
="http://schemas.microsoft.com/intellisense/ie5"
>
</
HEAD
>
<
body
>
<
form
id
="form1"
runat
="server"
>
<
div
><
FONT
face
="宋体"
></
FONT
>
</
div
>
</
form
>
</
body
>
</
HTML
>
生成验证码后台文件
using
System;
using
System.Collections;
using
System.Web;
using
System.Web.UI;
using
System.Web.UI.WebControls;
using
System.Drawing;
using
System.Drawing.Drawing2D;
namespace
GZPI.Gateway
{
///
<summary>
///
GenerateCheckCode 的摘要说明。
///
</summary>
public
class
GenerateCheckCode : System.Web.UI.Page
{
private
void
Page_Load(
object
sender, System.EventArgs e)
{
//
在此处放置用户代码以初始化页面
this
.CreateCheckCodeImage(GenerateCheckCodes(
4
));
}
#region
Web 窗体设计器生成的代码
override
protected
void
OnInit(EventArgs e)
{
//
//
CODEGEN: 该调用是 ASP.NET Web 窗体设计器所必需的。
//
InitializeComponent();
base
.OnInit(e);
}
///
<summary>
///
设计器支持所需的方法 - 不要使用代码编辑器修改
///
此方法的内容。
///
</summary>
private
void
InitializeComponent()
{
this
.Load
+=
new
System.EventHandler(
this
.Page_Load);
}
#endregion
private
string
GenerateCheckCodes(
int
iCount)
{
int
number;
string
checkCode
=
String.Empty;
int
iSeed
=
DateTime.Now.Millisecond;
System.Random random
=
new
Random(iSeed);
for
(
int
i
=
0
; i
<
iCount; i
++
)
{
number
=
random.Next(
10
);
checkCode
+=
number.ToString();
}
Session[
"
CheckCode
"
]
=
checkCode;
return
checkCode;
}
private
void
CreateCheckCodeImage(
string
checkCode)
{
if
(checkCode
==
null
||
checkCode.Trim()
==
String.Empty)
return
;
int
iWordWidth
=
15
;
int
iImageWidth
=
checkCode.Length
*
iWordWidth;
Bitmap image
=
new
Bitmap(iImageWidth,
20
);
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);
//
画图片的背景噪音点
for
(
int
i
=
0
; i
<
20
; 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);
}
//
画图片的背景噪音线
for
(
int
i
=
0
; i
<
2
; i
++
)
{
int
x1
=
0
;
int
x2
=
image.Width;
int
y1
=
random.Next(image.Height);
int
y2
=
random.Next(image.Height);
if
(i
==
0
)
{
g.DrawLine(
new
Pen(Color.Gray,
2
), x1, y1, x2, y2);
}
}
for
(
int
i
=
0
; i
<
checkCode.Length; i
++
)
{
string
Code
=
checkCode[i].ToString();
int
xLeft
=
iWordWidth
*
(i);
random
=
new
Random(xLeft);
int
iSeed
=
DateTime.Now.Millisecond;
int
iValue
=
random.Next(iSeed)
%
4
;
if
(iValue
==
0
)
{
Font font
=
new
Font(
"
Arial
"
,
13
, (FontStyle.Bold
|
System.Drawing.FontStyle.Italic));
Rectangle rc
=
new
Rectangle(xLeft,
0
, iWordWidth, image.Height);
LinearGradientBrush brush
=
new
LinearGradientBrush(rc, Color.Blue, Color.Red,
1.5f
,
true
);
g.DrawString(Code, font, brush, xLeft,
2
);
}
else
if
(iValue
==
1
)
{
Font font
=
new
System.Drawing.Font(
"
楷体
"
,
13
, (FontStyle.Bold));
Rectangle rc
=
new
Rectangle(xLeft,
0
, iWordWidth, image.Height);
LinearGradientBrush brush
=
new
LinearGradientBrush(rc, Color.Blue, Color.DarkRed,
1.3f
,
true
);
g.DrawString(Code, font, brush, xLeft,
2
);
}
else
if
(iValue
==
2
)
{
Font font
=
new
System.Drawing.Font(
"
宋体
"
,
13
, (System.Drawing.FontStyle.Bold));
Rectangle rc
=
new
Rectangle(xLeft,
0
, iWordWidth, image.Height);
LinearGradientBrush brush
=
new
LinearGradientBrush(rc, Color.Green, Color.Blue,
1.2f
,
true
);
g.DrawString(Code, font, brush, xLeft,
2
);
}
else
if
(iValue
==
3
)
{
Font font
=
new
System.Drawing.Font(
"
黑体
"
,
13
, (System.Drawing.FontStyle.Bold
|
System.Drawing.FontStyle.Bold));
Rectangle rc
=
new
Rectangle(xLeft,
0
, iWordWidth, image.Height);
LinearGradientBrush brush
=
new
LinearGradientBrush(rc, Color.Blue, Color.Green,
1.8f
,
true
);
g.DrawString(Code, font, brush, xLeft,
2
);
}
}
//////
画图片的前景噪音点
//
for (int i = 0; i < 8; 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.BinaryWrite(ms.ToArray());
}
finally
{
g.Dispose();
image.Dispose();
}
}
}
}
四、效果图展示
验证码数字
验证码数字+字母
验证码汉字