https://bugzilla.wikimedia.org/show_bug.cgi?id=6672

--- Comment #45 from Neil Kandalgaonkar <[email protected]> 2011-10-08 
02:19:22 UTC ---
Well, you are all commenting on related issues, but as for Flickr I can speak
authoritatively since I used to work there. And anyway, you could have verified
its behaviour pretty easily yourself.

I think this picture says it all. Here they are with our rotated test image:

   http://www.flickr.com/photos/brevity/6221434141/meta/in/photostream/

No, they did not do EXIF from day one. In fact, they don't do EXIF rotation at
all, and EXIF metadata is entirely stripped from all scaled images. 

The reason why is that some people stuff ridiculous amounts of data in there,
which is then incompressible. So if they preserved EXIF there would be some
idiot who would just have to add 1MB of data into there, and then suddenly the
75x75 version is still 1MB, which breaks some other code, etc. etc. At Flickr
they will add (some) EXIF info to the metadata of the file, which you can view
on the metadata page.

So, Flickr doesn't have this problem because they don't do anything with EXIF.
But even if they *did* change their system, it would still be mostly okay. At
Flickr, when a file is uploaded, it makes several thumbnails at fixed sizes and
then that is it. Unless the file is replaced or manually rotated it never makes
another thumbnail. 

Commons is very different; it will generate any thumbnail of any size on
demand, and doesn't generate thumbnails until asked.

So, on Flickr, if you uploaded some file in 2007, and you got it to the point
where you like the rotation of the file or the thumbnails, it will stay that
way. 

However, at Commons, now a file that was manually rotated in 2007 could be
thumbnailed with the new code, which tries to EXIF-rotate. So now you have
thumbnails that were created with different code all co-existing.

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