; Funktion: _GetJpegSize()
; Liest die Größeninformationen eines Bildes aus
Func _GetJpegSize($file)
Local $size[2]
Local $fs, $pos = 3

if not (_FileReadAtOffsetHEX ($file, 1, 2) = "FFD8") then
    SetError(1); Not Jpeg
    Return("")
endif

$fs = FileGetSize($file)

While $pos < $fs
    $data = _FileReadAtOffsetHEX ($file, $pos, 4)
    if StringLeft($data, 2) = "FF" then; Valid segment start
        if StringInStr("C0 C2 CA C1 C3 C5 C6 C7 C9 CB CD CE CF", StringMid($data, 3, 2)) then; Segment with size data
           $seg = _FileReadAtOffsetHEX ($file, $pos+5, 4)
           $size[1] = Dec(StringLeft($seg, 4))
           $size[0] = Dec(StringRight($seg, 4))
           Return($size)
        else
           $pos = $pos + Dec(StringRight($data, 4)) + 2
        endif
    else
        exitloop
    endif
Wend
SetError(2); Segment not found
Return("")
EndFunc

Func _FileReadAtOffsetHEX ($file, $offset, $bytes)
    Local $tfile = FileOpen($file, 0)
    Local $tstr = ""
    FileRead($tfile, $offset-1)
    For $i = $offset To $offset + $bytes - 1
        $tstr =  $tstr & Hex(Asc(FileRead($tfile, 1)), 2)
    Next
    FileClose($tfile)
    Return ($tstr)
Endfunc