Calculate height and width of GIF/JPG files

Calculate height and width of GIF/JPG files(4)                header = Input(3, f)
               ' Next two bytes are the height of the image
               header = Input(2, f)
               hHi = Asc(Midbp(header, 1, 1))
               hLo = Asc(Midbp(header, 2, 1))
               h = hHi * 256 + hLo
               ' Next two bytes are the width of the image
               header = Input(2, f)
               wHi = Asc(Midbp(header, 1, 1))
               wLo = Asc(Midbp(header, 2, 1))
               w = wHi * 256 + wLo
               foundMarker = True     ' Exit the while loop
            Else   ' It's not one of the special markers - skip over it