The downloaded album art seems to all be plain old JPEG wrapped in some proprietary junk. GraphicConverter, for one, can extract the images easily.
The stuff going into the new local folder seems to be mostly PNG, also with gunk on top. I haven't got around to seeing what off-the-shelf software, if any, can extract it. A search for a PNG header may be reliable enough without deciphering the iTunes preamble.
(edit: Ooo, but it's still in the applescript dictionary, so this may not be so bad at all.)
The stuff going into the new local folder seems to be mostly PNG, also with gunk on top. I haven't got around to seeing what off-the-shelf software, if any, can extract it. A search for a PNG header may be reliable enough without deciphering the iTunes preamble.
(edit: Ooo, but it's still in the applescript dictionary, so this may not be so bad at all.)