一个获取图片宽度和高度的类

程序代码：
<%
Class ImgWHInfo ‘获取图片宽度和高度的类，支持JPG，GIF，PNG，BMP
    Dim ASO
    Private Sub Class_Initialize
        Set ASO=Server.CreateObject("ADODB.Stream")
        ASO.Mode=3
        ASO.Type=1
        ASO.Open
    End Sub
    Private Sub Class_Terminate
        Err.Clear
        Set ASO=Nothing
    End Sub

    Private Function Bin2Str(Bin)
        Dim I, Str
        For I=1 To LenB(Bin)
            clow=MidB(Bin,I,1)
            If ASCB(clow)<128 Then
                Str = Str & Chr(ASCB(clow))
            Else
                I=I+1
                If I <= LenB(Bin) Then Str = Str & Chr(ASCW(MidB(Bin,I,1)&clow))
            End If
        Next
        Bin2Str = Str
    End Function
      
    Private Function Num2Str(Num,Base,Lens)
        Dim Ret
        Ret = ""
        While(Num>=Base)
            Ret = (Num Mod Base) & Ret
            Num = (Num – Num Mod Base)/Base
        Wend
        Num2Str = Right(String(Lens,"0") & Num & Ret,Lens)
    End Function
      
    Private Function Str2Num(Str,Base)
        Dim Ret,I
        Ret = 0
        For I=1 To Len(Str)
            Ret = Ret *base + Cint(Mid(Str,I,1))
        Next
        Str2Num=Ret
    End Function
      
    Private Function BinVal(Bin)
        Dim Ret,I
        Ret = 0
        For I = LenB(Bin) To 1 Step -1
            Ret = Ret *256 + AscB(MidB(Bin,I,1))
        Next
        BinVal=Ret
    End Function
      
    Private Function BinVal2(Bin)
        Dim Ret,I
        Ret = 0
        For I = 1 To LenB(Bin)
            Ret = Ret *256 + AscB(MidB(Bin,I,1))
        Next
        BinVal2=Ret
    End Function
      
    Private Function GetImageSize(filespec)
        Dim bFlag
        Dim Ret(3)
        ASO.LoadFromFile(filespec)
        bFlag=ASO.Read(3)
        Select Case Hex(binVal(bFlag))
        Case "4E5089":
            ASO.Read(15)
            ret(0)="PNG"