源码，保存为CodePhoto.asp,
在要插入验证码图片的地方插入<img border="0" src="codephoto.asp" width="50" height="20">
生成的随机验证码存在
Session("ValidCode")中，你只要把用户输入的验证码和Session("ValidCode")比较就行了。
<%
Call Com_CreatValidCode("ValidCode")
response.write vCodes
Sub Com_CreatValidCode(pSN)
' 禁止缓存
Response.Expires = -9999
Response.AddHeader "Pragma","no-cache"
Response.AddHeader "cache-ctrol","no-cache"
Response.ContentType = "Image/BMP"
Randomize
Dim i, ii, iii
Const cOdds = 2 ' 杂点出现的机率
Const cAmount = 36 ' 文字数量
Const cCode = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
' 颜色的数据(字符，背景)
Dim vColorData(1)
vColorData(0) = ChrB(255) & ChrB(100) & ChrB(0) ' 蓝0，绿0，红0（黑色）
vColorData(1) = ChrB(255) & ChrB(255) & ChrB(255) ' 蓝250，绿236，红211（浅蓝色）
' 随机产生字符
Dim vCode(4), vCodes
For i = 0 To 3
vCode(i) = Int(Rnd * cAmount)
vCodes = vCodes & Mid(cCode, vCode(i) + 1, 1)
Next
Session("ValidCode") = vCodes '记录入Session
' 字符的数据
Dim vNumberData(35)
vNumberData(0) = "1110000111110111101111011110111101001011110100101111010010111101001011110111101111011110111110000111"
vNumberData(1) = "1111011111110001111111110111111111011111111101111111110111111111011111111101111111110111111100000111"
vNumberData(2) = "1110000111110111101111011110111111111011111111011111111011111111011111111011111111011110111100000011"
vNumberData(3) = "1110000111110111101111011110111111110111111100111111111101111111111011110111101111011110111110000111"
vNumberData(4) = "1111101111111110111111110011111110101111110110111111011011111100000011111110111111111011111111000011"
vNumberData(5) = "1100000011110111111111011111111101000111110011101111111110111111111011110111101111011110111110000111"
vNumberData(6) = "1111000111111011101111011111111101111111110100011111001110111101111011110111101111011110111110000111"
vNumberData(7) = "1100000011110111011111011101111111101111111110111111110111111111011111111101111111110111111111011111"
vNumberData(8) = "1110000111110111101111011110111101111011111000011111101101111101111011110111101111011110111110000111"
vNumberData(9) = "1110001111110111011111011110111101111011110111001111100010111111111011111111101111011101111110001111"
vNumberData(10) = "1111011111111101111111101011111110101111111010111111101011111100000111110111011111011101111000100011"
vNumberData(11) = "1000000111110111101111011110111101110111110000111111011101111101111011110111101111011110111000000111"
vNumberData(12) = "1110000011110111101110111110111011111111101111111110111111111011111111101111101111011101111110001111"
vNumberData(13) = "1000001111110111011111011110111101111011110111101111011110111101111011110111101111011101111000001111"
vNumberData(14) = "1000000111110111101111011011111101101111110000111111011011111101101111110111111111011110111000000111"
vNumberData(15) = "1000000111110111101111011011111101101111110000111111011011111101101111110111111111011111111000111111"
vNumberData(16) = "1110000111110111011110111101111011111111101111111110111111111011100011101111011111011101111110001111"
vNumberData(17) = "1000100011110111011111011101111101110111110000011111011101111101110111110111011111011101111000100011"
vNumberData(18) = "1100000111111101111111110111111111011111111101111111110111111111011111111101111111110111111100000111"
vNumberData(19) = "1110000011111110111111111011111111101111111110111111111011111111101111111110111110111011111000011111"
vNumberData(20) = "1000100011110111011111011011111101011111110001111111010111111101101111110110111111011101111000100011"
vNumberData(21) = "1000111111110111111111011111111101111111110111111111011111111101111111110111111111011110111000000011"
vNumberData(22) = "1000100011110010011111001001111100100111110101011111010101111101010111110101011111010101111001010011"
vNumberData(23) = "1000100011110011011111001101111101010111110101011111010101111101100111110110011111011001111000110111"
vNumberData(24) = "1110001111110111011110111110111011111011101111101110111110111011111011101111101111011101111110001111"
vNumberData(25) = "1000000111110111101111011110111101111011110000011111011111111101111111110111111111011111111000111111"
vNumberData(26) = "1110001111110111011110111110111011111011101111101110111110111011111011101001101111011001111110001011"
vNumberData(27) = "1000001111110111011111011101111101110111110000111111010111111101101111110110111111011101111000110011"
vNumberData(28) = "1110000011110111101111011110111101111111111001111111111001111111111011110111101111011110111100000111"
vNumberData(29) = "1000000011101101101111110111111111011111111101111111110111111111011111111101111111110111111110001111"
vNumberData(30) = "1000100011110111011111011101111101110111110111011111011101111101110111110111011111011101111110001111"
vNumberData(31) = "1000100011110111011111011101111101110111111010111111101011111110101111111010111111110111111111011111"
vNumberData(32) = "1001010011110101011111010101111101010111110101011111001001111110101111111010111111101011111110101111"
vNumberData(33) = "1000100011110111011111101011111110101111111101111111110111111110101111111010111111011101111000100011"
vNumberData(34) = "1000100011110111011111011101111110101111111010111111110111111111011111111101111111110111111110001111"
vNumberData(35) = "1100000011110111011111111101111111101111111110111111110111111111011111111011111111101110111100000011"
' 输出图像文件头
Response.BinaryWrite ChrB(66) & ChrB(77) & ChrB(230) & ChrB(4) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) &_
ChrB(0) & ChrB(0) & ChrB(54) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(40) & ChrB(0) &_
ChrB(0) & ChrB(0) & ChrB(40) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(10) & ChrB(0) &_
ChrB(0) & ChrB(0) & ChrB(1) & ChrB(0)
' 输出图像信息头
Response.BinaryWrite ChrB(24) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(176) & ChrB(4) &_
ChrB(0) & ChrB(0) & ChrB(18) & ChrB(11) & ChrB(0) & ChrB(0) & ChrB(18) & ChrB(11) &_
ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) &_
ChrB(0) & ChrB(0)
For i = 9 To 0 Step -1 ' 历经所有行
For ii = 0 To 3 ' 历经所有字
For iii = 1 To 10 ' 历经所有像素
' 逐行、逐字、逐像素地输出图像数据
If Rnd * 100 + 1 < cOdds Then ' 随机生成杂点
Response.BinaryWrite vColorData(0)
Else
Response.BinaryWrite vColorData(Mid(vNumberData(vCode(ii)), i * 10 + iii, 1))
End If
Next
Next
Next
End Sub
%>