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User Tips: Reading Flash File Information (.swf) through an ASP Page

With the number of Web sites using Macromedia Flash Files (.swf files) to present content, as a Web developer it may come in handy to have an ASP page that could easily read various tidbits of information about a Flash file. Fortunately, Flash files save a plethora of useful information in their headers. This information can be read using the FileSystemObject through an ASP page! (To learn more about Flash, check out FlashKit.com!)

In order to ease the process of reading this information, I created a handy class to do the grunt work for me. (For more information on using classes with VBScript, be sure to read: Using Classes within VBScript.) The class I created returns the following information about a Flash file:

SWFDump Class

Property Description

Version The version of the Flash file (3,4 or 5 at the moment)

Height Expresed in pixels.

Width Expresed in pixels.

xMin Expresed in Twips (20 twips = 1 pixel)

xMax Expresed in Twips

yMin Expresed in Twips

yMax Expresed in Twips

FileSize The total size of the .swf file.

FrameRate How many frames are in the Flash file.

FrameCounter Frame counter information.

The use of the SWFDump class is very simple. First off, I recommend that you place it in an include file so that you can easily include the class in the files that need to read Flash file information. (For more information on server-side includes be sure to read: The Low-Down on #include.) I chose to name my include file swfheaderdump.inc. To use the class, simply use code like the following:

<% '------------------------------------------------------------- ' Create Date : 17/10/2001 (dd/mm/yyyy) ' Mod. Date : 17/10/2001 ' Author : Claudio Heidel (heidel@f256.com) '------------------------------------------------------------- ' Pass the SWF name in querystring this way ' swfdump.asp?swf=yourmovie.swf set myObj = new swfdump myObj.SWFDump (Server.MapPath(request("swf"))) Response.Write "Heigt (pixel) = " & myObj.Heigt & " " Response.Write "Width (pixel) = " & myObj.Width & " " Response.Write "Version = " & myObj.Version & " " Response.Write "FileLen (bytes) = " & myObj.FileLen & " " Response.Write "xMin (twips) = " & myObj.xMin & " " Response.Write "xMax (twips) = " & myObj.xMax & " " Response.Write "yMin (twips) = " & myObj.yMin & " " Response.Write "yMax (twips) = " & myObj.yMax & " " Response.Write "FrameRate = " & myObj.FrameRate & " " Response.Write "FrameCount = " & myObj.FrameCount & " " %>

Simple enough. The file swfheaderdump.inc needs to contain the full definition of the SWFDump class:

<% '------------------------------------------------------------- ' Create Date : 17/10/2001 (dd/mm/yyyy) ' Mod. Date : 17/10/2001 ' Author : Claudio Heidel (heidel@f256.com) '------------------------------------------------------------- Class SWFDump Private header Private RECTdata Private nBits Private mversion Private mfilelen Private mxMin Private mxMax Private myMin Private myMax Private mheigt Private mwidth Private mframerate Private mframecount Private Sub Class_Initialize() End Sub Private Sub Class_Terminate() End Sub Private Function ReadHeader (filename) Const ForReading = 1, ForWriting = 2, ForAppending = 8 Dim fso, f Set fso = CreateObject("Scripting.FileSystemObject") Set f = fso.OpenTextFile(filename, ForReading) ReadHeader = f.Read(21) End Function Private Function ToBin(inNumber, OutLenStr ) Dim binary binary = "" do while inNumber >= 1 binary = binary & inNumber mod 2 inNumber = inNumber \ 2 loop binary = binary & String(OutLenStr - len(binary), "0") ToBin = StrReverse(binary) End Function Private Function Bin2Decimal(inBin) Dim counter Dim temp Dim Value inBin = StrReverse(inBin) temp = 0 For counter = 1 to Len(inBin) If counter = 1 then Value = 1 Else Value = Value * 2 End If temp = temp + mid(inBin, counter ,1) * Value Next Bin2Decimal = temp End Function Public Function SWFDump(fileName) header = ReadHeader (fileName) mversion = asc(mid(header,4,1)) mfilelen = asc(mid(header,5,1)) mfilelen = mfilelen + asc(mid(header,6,1)) * 256 mfilelen = mfilelen + asc(mid(header,7,1)) * 256 * 256 mfilelen = mfilelen + asc(mid(header,8,1)) * 256 * 256 * 256 RECTdata = ToBin(asc(mid(header,9,1)),8) RECTdata = RECTdata & ToBin(asc(mid(header,10,1)),8) RECTdata = RECTdata & ToBin(asc(mid(header,11,1)),8) RECTdata = RECTdata & ToBin(asc(mid(header,12,1)),8) RECTdata = RECTdata & ToBin(asc(mid(header,13,1)),8) RECTdata = RECTdata & ToBin(asc(mid(header,14,1)),8) RECTdata = RECTdata & ToBin(asc(mid(header,15,1)),8) RECTdata = RECTdata & ToBin(asc(mid(header,16,1)),8) RECTdata = RECTdata & ToBin(asc(mid(header,17,1)),8) nBits = Mid(RECTdata,1,5) nBits = Bin2Decimal(nBits) mxMin = Bin2Decimal(Mid(RECTdata,6,nBits)) mxMax = Bin2Decimal(Mid(RECTdata,6 + nBits * 1 ,nBits)) myMin = Bin2Decimal(Mid(RECTdata,6 + nBits * 2 ,nBits)) myMax = Bin2Decimal(Mid(RECTdata,6 + nBits * 3 ,nBits)) mheigt = (myMax - myMin) / 20 mwidth = (mxMax - mxMin) / 20 mframerate = asc(mid(header,18,1)) mframecount = asc(mid(header,19,1)) mframecount = mframecount + asc(mid(header,20,1)) * 256 End Function Public Property Get Heigt() Heigt = mheigt End Property Public Property Get Width() Width = mwidth End Property Public Property Get Version() Version = mversion End Property Public Property Get FileLen() FileLen = mfilelen End Property Public Property Get xMin() xMin = mxMin End Property Public Property Get xMax() xMax = mxMax End Property Public Property Get yMin() yMin = myMin End Property Public Property Get yMax() yMax = myMax End Property Public Property Get Framerate() Framerate = mframerate End Property Public Property Get Framecount() Framecount = mframecount End Property End Class %>

I hope you find this contribution useful and handy! If anybody has any questions please email me at heidel@f256.com or visit http://www.f256.com

Happy Programming!

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