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Wednesday, August 18, 2010


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JPEG rotation isn't lossless unless a specific set of conditions are met ( http://www.faqs.org/faqs/jpeg%2Dfaq/part1/index.html ). It's kind of a hack that JPEGs could be rotated losslessly at all. EXIF seems a much cleaner and less destructive way to do rotations for compressed images.


i think virtually all cameras fit the constraints on images sizes to allow lossless JPEG rotation, and EXIF is just not part of JPEG, it's an independent add-on. in an ideal world, cameras would store the sensor dump in raw as retrieved from the sensor, but JPEGs always would be rotated internally. EXIF then could be used to capture the fact that the image had been rotated for JPEG encoding. i am wondering whether there is any camera out there that does it like this, but i guess EXIF does not even have the appropriate fields to support this kind of scenario.

practically speaking, i am simply annoyed that after three years of working just fine, i now have people telling me that i am sending them pictures in the wrong orientation. technically speaking i may have the moral upper hand, but it makes little sense for me to tell them that they should dump their email clients and switch to one that works as apple thinks it should work.


I wrote a free open source JPEG auto rotator windows explorer context menu extension that rotates the image according to the EXIF orientation property. Also a command line version. I was motivated to write this after trying to show slideshows on various devices (TVs, digital picture frames) that didn't respect the orientation property and since other windows explorer context menu extensions that did this had some limitations


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