高手请进,GIF/JPG文件如何通过程序得知图片的尺寸?

我想在网站中添加图片上传的功能,可是尺寸不能太大,可我又不知道该如何得到图片的尺寸,谁能帮我?/???
希望能给出代码,高分相送!!

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 1<html><head>
 2<script>   
 3  
 4function getImageDimension (imgURL, loadHandler) {   
 5var img = new Image();   
 6img.onload = loadHandler;   
 7if (document.layers && location.protocol.toLowerCase() != 'file:' && navigator.javaEnabled())   
 8netscape.security.PrivilegeManager.enablePrivilege( 'UniversalFileRead'   
 9); img.src = imgURL;}   
10function showImageDimensions () {   
11alert(this.width + 'x' + this.height);}   
12</script>
13<script>   
14function checkImageDimensions (fileName) {   
15var imgURL = 'file:///' + fileName;   
16getImageDimension(imgURL, showImageDimensions);}   
17</script>
18</head><body>
19<form name="formName"><input name="fileName" type="file"/><br/>
20<input onclick="checkImageDimensions(this.form.fileName.value)" type="button" value="check image dimensions"/></form></body>
21</html>

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 1<head>
 2<script>   
 3function getImageDimension(imgURL, loadHandler){   
 4var img = new Image();   
 5img.onload = loadHandler;   
 6if (document.layers && location.protocol.toLowerCase() != 'file:' && navigator.javaEnabled())   
 7netscape.security.PrivilegeManager.enablePrivilege('UniversalFileRead');   
 8img.src = imgURL;   
 9}   
10function showImageDimensions()   
11{   
12alert(this.width + 'x' + this.height);   
13}   
14function checkImageDimensions (fileName) {   
15var imgURL = 'file:///' + fileName;   
16getImageDimension(imgURL, showImageDimensions);}   
17</script>
18</head>
1<body>
2<form name="formName"><input name="fileName" type="file"/><br/>
3<input onclick="checkImageDimensions(this.form.fileName.value)" type="button" value="检查图片尺寸"/></form></body>

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<%
':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
'::: BMP, GIF, JPG and PNG :::
':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
':::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
'::: :::
'::: 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))

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