On Mar 7, 2014, at 5:00 AM, [email protected] wrote:
> All I'm looking for is a way to get the poster frame of a video (if it
> exists) without QuickTime. Likewise, I just need a way to check if a
> FolderItem is a picture, again without using QuickTime.
>
> I'm probably misunderstanding something...
In a project that I did a while back I needed to get the dimensions of graphics
files. As you probably know this information is stored differently for each
graphic type. The one good thing though is that it is common that the first
four bytes of a graphic file can be used to determine what kind of graphic file
it is and once knowing that the proper code can be used to obtain the
dimensions of that graphic.
The following code is used to determine which graphic format the file is. Once
determined it calls the analyseXXX method that will get the dimensions of that
graphic. It works for BMP, GIF, JPG, PNG, TIF and PICT files. IF you need other
graphic types I imagine you could find the specs for that file type and add the
proper check of the first four bytes to the following code.
The graphic file is opened as a binary stream file in order to read the first
four bytes into a UInt32 property.
fileIdent is a Uint32 property.
You should be able to use this to come up with code for your project to
identify graphics file types.
bs = BinaryStream.Open(f, False)
if bs = nil then
s = "Unable to open the selected file """ + f.name + " in the
analyseGraphic method"
showAlertDialog kPgmErr, s, "Okay", "", "", "a", "", 0
Return
end if
fileIdent = bs.readUint32 // read first four bytes from the file
firstFour = Right("0000000" + hex(fileIdent), 8)
if left(firstFour, 4) = "424D" then // first two bytes 424D (BM) a BMP file?
analyseBMP
else
select case firstFour
case "47494638" // test if first four bytes are &h47494638 (GIF8) a GIF
file
analyseGIF
case "FFD8FFE0" // test if first four bytes are &hFFD8FFE0 for a JPG file
analyseJPG
case "FFD8FFE1"
analyseJPG
case "89504E47" // test if first four bytes are &h89504E47 for a PNG file
analysePNG
case "4D4D002A" // is this one of the TIF identifiers?
analyseTIF
case "49492A00" // is this the other TIF identifier?
bs.LittleEndian = true // this TIF format has low byte first
analyseTIF
case "00000000" // does this look like a PICT file can't find any written
spec for PICT
analysePCT
else
imageKind = "?" // not a known image file
end Select
end if
bs.Close
=== An Apple addict in Tennessee ===
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