We should be able to automaticaly detect when a file has been rotated
without updating the exif data most of the time. Exif stores the image
width and height a couple of times. Cant we just check if the
width/height in the exif match the widht/height of the actual image?
The only cases this wont catch is bottom-right orientation (should be
very rare) and cameras with square sensors(are there any?).
If the width/height tags are getting molested by the gimp, then we could
fall back to comparing against the aspect ratio of the embedded preview
when there is one.
On a more practical note, gimp seems to completely throw away any exif
data when saving as a jpg(tested in 1.3,24, and 2.2.2). Perhaps this is
less of a problem than it has been made out to be (or perhaps I have
weird cvs versions of gimp installed).
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