Calculate height and width of GIF/JPG files

Calculate height and width of GIF/JPG files(5)                header = Input(2, f)   ' Next two bytes are the marker length
               wHi = Asc(Midbp(header, 1, 1))
               wLo = Asc(Midbp(header, 2, 1))
               w = wHi * 256 + wLo
               header = Input(w-2, f) ' Skip over that many bytes (minus the 2 byte length already read)
               w = 0   ' Clear the variable
            End If
         Wend   ' Continue until the marker is found
      End If    ' Ends the check to see if the file starts with FF D8
EndOfFile:
      If Err <> 0 Then
         Err = 0
         Resume AfterError
      End If
   End If   ' Ends the check to see if the format is GIF or JPG