* 说  明：自己项目中用到的图片验证码，感觉还不错

numcode.asp

 程序代码
<%@CodePage="65001"%>
<%
Call Com_CreatValidCode("GetCode")

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 = 4 ' 杂点出现的机率
    Const cAmount = 13 ' 文字数量
    Const cCode = "0123456789+=?"

    ' 颜色的数据(字符，背景)
    Dim vColorData(1),vColorRandom(10)
    'vColorData(0) = ChrB(Int(Rnd*155)+100) & ChrB(Int(Rnd*155)+100) & ChrB(Int(Rnd*155)+100) ' 蓝0，绿0，红0（黑色）
    vColorRandom(0)=ChrB(150) & ChrB(0) & ChrB(0)
    vColorRandom(1)=ChrB(0) & ChrB(150) & ChrB(0)
    vColorRandom(2)=ChrB(0) & ChrB(0) & ChrB(150)
    vColorRandom(3)=ChrB(0) & ChrB(50) & ChrB(150)
    vColorRandom(4)=ChrB(150) & ChrB(50) & ChrB(0)
    vColorRandom(5)=ChrB(150) & ChrB(0) & ChrB(150)
    vColorRandom(6)=ChrB(150) & ChrB(100) & ChrB(10)
    vColorRandom(7)=ChrB(150) & ChrB(40) & ChrB(120)
    vColorRandom(8)=ChrB(150) & ChrB(0) & ChrB(250)
    vColorRandom(9)=ChrB(100) & ChrB(100) & ChrB(100)
    vColorRandom(10)=ChrB(50) & ChrB(50) & ChrB(50)
    vColorData(0) = vColorRandom(0)            '初始化字符颜色，随机生成
    vColorData(1) = ChrB(250) & ChrB(250) & ChrB(255) '背景色 蓝250，绿236，红211（浅蓝色）
    ' 随机产生字符
    Dim vCode(6),vCodes,vCodeColors(6)
    For i = 0 To 6
        vCodeColors(i)=vColorRandom(Int(Rnd * 10))
    Next
    
    vCode(0) = Int(Rnd*8)+1
    vCode(1) = Int(Rnd*9)
    vCode(2) = 10                   ' + 号
    vCode(3) = Int(Rnd*8)+1
    vCode(4) = Int(Rnd*9)
    vCode(5) = 11                    ' = 号
    vCode(6) = 12                    ' ? 号
    Session(pSN) = vCode(0)*10+vCode(1)+vCode(3)*10+vCode(4) '记录入Session
    ' 字符的数据
    Dim vNumberData(12)

    ' 输出图像信息头
    Response.BinaryWrite ChrB(24) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(112) & ChrB(8) &_
    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 6 ' 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
                vColorData(0)=vCodeColors(ii)
                If Rnd * 99 + 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
    Response.BinaryWrite vColorData(1) & vColorData(1)
    Next
End Sub

%>

调用：

 程序代码
<img src='numcode.asp' align='absmiddle' border='0'>

提交验证：

 程序代码
if request("act")="check" then
   if cstr(session("GetCode"))<>cstr(request("checkcode")) then
      response.write "验证码错误"
      response.end
   end if
end if