Here is a generic set of functions I found ages ago for getting information on an image. I'll put the way I've been using it at the end.
':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::'
'::: :::'
'::: This routine will attempt to identify any filespec passed :::'
'::: as a graphic file (regardless of the extension). This will :::'
'::: work with BMP, GIF, JPG and PNG files. :::'
'::: :::'
':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::'
'::: Based on ideas presented by David Crowell :::'
'::: (credit where due) :::'
':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::'
':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::'
':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::'
'::: blah blah blah blah blah blah blah blah blah blah blah blah :::'
'::: blah blah blah blah blah blah blah blah blah blah blah blah :::'
'::: blah blah Copyright *c* MM, Mike Shaffer blah blah :::'
'::: blah blah ALL RIGHTS RESERVED WORLDWIDE blah blah :::'
'::: blah blah Permission is granted to use this code blah blah :::'
'::: blah blah in your projects, as long as this blah blah :::'
'::: blah blah copyright notice is included blah blah :::'
'::: blah blah blah blah blah blah blah blah blah blah blah blah :::'
'::: blah blah blah blah blah blah blah blah blah blah blah blah :::'
':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::'
':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::'
'::: :::'
'::: This function gets a specified number of bytes from any :::'
'::: file, starting at the offset (base 1) :::'
'::: :::'
'::: Passed: :::'
'::: flnm => Filespec of file to read :::'
'::: offset => Offset at which to start reading :::'
'::: bytes => How many bytes to read :::'
'::: :::'
':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::'
function GetBytes(flnm, offset, bytes)
Dim objFSO
Dim objFTemp
Dim objTextStream
Dim lngSize
on error resume next
Set objFSO = CreateObject("Scripting.FileSystemObject")
' First, we get the filesize'
Set objFTemp = objFSO.GetFile(flnm)
lngSize = objFTemp.Size
set objFTemp = nothing
fsoForReading = 1
Set objTextStream = objFSO.OpenTextFile(flnm, fsoForReading)
if offset > 0 then
strBuff = objTextStream.Read(offset - 1)
end if
if bytes = -1 then ' Get All!'
GetBytes = objTextStream.Read(lngSize) 'ReadAll'
else
GetBytes = objTextStream.Read(bytes)
end if
objTextStream.Close
set objTextStream = nothing
set objFSO = nothing
end function
':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::'
'::: :::'
'::: Functions to convert two bytes to a numeric value (long) :::'
'::: (both little-endian and big-endian) :::'
'::: :::'
':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::'
function lngConvert(strTemp)
lngConvert = clng(asc(left(strTemp, 1)) + ((asc(right(strTemp, 1)) * 256)))
end function
function lngConvert2(strTemp)
lngConvert2 = clng(asc(right(strTemp, 1)) + ((asc(left(strTemp, 1)) * 256)))
end function
':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::'
'::: :::'
'::: This function does most of the real work. It will attempt :::'
'::: to read any file, regardless of the extension, and will :::'
'::: identify if it is a graphical image. :::'
'::: :::'
'::: Passed: :::'
'::: flnm => Filespec of file to read :::'
'::: width => width of image :::'
'::: height => height of image :::'
'::: depth => color depth (in number of colors) :::'
'::: strImageType=> type of image (e.g. GIF, BMP, etc.) :::'
'::: :::'
':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::'
function gfxSpex(flnm, width, height, depth, strImageType)
dim strPNG
dim strGIF
dim strBMP
dim strType
strType = ""
strImageType = "(unknown)"
gfxSpex = False
strPNG = chr(137) & chr(80) & chr(78)
strGIF = "GIF"
strBMP = chr(66) & chr(77)
strType = GetBytes(flnm, 0, 3)
if strType = strGIF then ' is GIF'
strImageType = "GIF"
Width = lngConvert(GetBytes(flnm, 7, 2))
Height = lngConvert(GetBytes(flnm, 9, 2))
Depth = 2 ^ ((asc(GetBytes(flnm, 11, 1)) and 7) + 1)
gfxSpex = True
elseif left(strType, 2) = strBMP then ' is BMP'
strImageType = "BMP"
Width = lngConvert(GetBytes(flnm, 19, 2))
Height = lngConvert(GetBytes(flnm, 23, 2))
Depth = 2 ^ (asc(GetBytes(flnm, 29, 1)))
gfxSpex = True
elseif strType = strPNG then ' Is PNG'
strImageType = "PNG"
Width = lngConvert2(GetBytes(flnm, 19, 2))
Height = lngConvert2(GetBytes(flnm, 23, 2))
Depth = getBytes(flnm, 25, 2)
select case asc(right(Depth,1))
case 0
Depth = 2 ^ (asc(left(Depth, 1)))
gfxSpex = True
case 2
Depth = 2 ^ (asc(left(Depth, 1)) * 3)
gfxSpex = True
case 3
Depth = 2 ^ (asc(left(Depth, 1))) '8'
gfxSpex = True
case 4
Depth = 2 ^ (asc(left(Depth, 1)) * 2)
gfxSpex = True
case 6
Depth = 2 ^ (asc(left(Depth, 1)) * 4)
gfxSpex = True
case else
Depth = -1
end select
else
strBuff = GetBytes(flnm, 0, -1) ' Get all bytes from file'
lngSize = len(strBuff)
flgFound = 0
strTarget = chr(255) & chr(216) & chr(255)
flgFound = instr(strBuff, strTarget)
if flgFound = 0 then
exit function
end if
strImageType = "JPG"
lngPos = flgFound + 2
ExitLoop = false
do while ExitLoop = False and lngPos < lngSize
do while asc(mid(strBuff, lngPos, 1)) = 255 and lngPos < lngSize
lngPos = lngPos + 1
loop
if asc(mid(strBuff, lngPos, 1)) < 192 or asc(mid(strBuff, lngPos, 1)) > 195 then
lngMarkerSize = lngConvert2(mid(strBuff, lngPos + 1, 2))
lngPos = lngPos + lngMarkerSize + 1
else
ExitLoop = True
end if
loop
if ExitLoop = False then
Width = -1
Height = -1
Depth = -1
else
Height = lngConvert2(mid(strBuff, lngPos + 4, 2))
Width = lngConvert2(mid(strBuff, lngPos + 6, 2))
Depth = 2 ^ (asc(mid(strBuff, lngPos + 8, 1)) * 8)
gfxSpex = True
end if
end if
end function
I've been using it to generate a randomized XML file for an image library. The script only gets run when I finish uploading a new image to the library.
Here's the usage: (or at least how I used it)
'collect the image information into an array'
Dim blnGfxSpex, width, height, colors, strType
intCount = 0
For Each objFile In objFS.GetFolder(".\images").Files
If LCase(Right(objFile.Name, 4)) = ".jpg" and intCount <= intNumOfFiles Then
blnGfxSpex = gfxSpex((".\images\" & objFile.Name), width, height, colors, strType)
arrImages(intCount) = "<image>" & vbNewLine & _
"<filename>" & objFile.Name & "</filename>" & vbNewLine & _
"<caption></caption>" & vbNewLine & _
"<width>" & width & "</width>" & vbNewLine & _
"<height>" & height & "</height>" & vbNewLine & _
"</image>" & vbNewLine
intCount = intCount + 1
End If
Next
As you can see, I'm initializing the variables for width, height, etc. and the function sets them as appropriate. I know it's not kosher to use global variables like that, but it works.
Performance isn't as bad as you would think. In this particular case I am filtering the image library to just JPGs, but that is due to a limitation in the image library the XML is for, not due to a limitation in the functions.