[PYTHON IMAGE-SIG] ImageChops bug?

[Skip Montanaro]

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I tried taking the difference of two GIF images:

    >>> im1 = Image.open('mapwireworld.gif')
    >>> im2 = Image.open('mapwireworld.gif.GIF')
    >>> diff = ImageChops.difference(im1, im2)
    >>> Image._showxv(diff)
    Traceback (innermost last):
      File "<stdin>", line 1, in ?
      File "/usr/local/lib/python1.4/Image.py", line 544, in _showxv
	file = self.convert("RGB")._dump()
      File "/usr/local/lib/python1.4/Image.py", line 181, in convert
	im = self.im.convert(mode)
    ValueError: No palette
    >>> 

Why no palette?  The two original images are available at:

    http://dolphin.automatrix.com/~skip/mapwireworld.gif
    http://dolphin.automatrix.com/~skip/mapwireworld.gif.GIF

File says:

    mapwireworld.gif:     GIF picture - version 89a 599 x 455, 256 colors
    mapwireworld.gif.GIF: GIF picture - version 87a 599 x 455, interlaced, 64 colors

If I convert them to RGB images before taking their difference, the
difference image displays fine.  Seems like a bug in ImageChops.difference
or its underlying helper functions.  (This is PIL 0.2b5, by the way.)

Thx,

- -- 
Skip Montanaro     | Musi-Cal: http://concerts.calendar.com/
skip@calendar.com  | What's your favorite programming language? Mine's
(518)372-5583      | Python: http://www.python.org/

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