CAFxX/ImageTweak — Issue #21: Rotate the image according to its Orientation tag by default
Author: aleksejrs
Created: 2011-12-15 18:38:10+00:00
State: open

The EXIF tag “Orientation” specifies that the image is to be displayed rotated, and how.

It is usually used by cameras, because it takes less resources to change the tag than to rotate the image. But it is also useful without resource constraints, because rotation of the actual image data in a JPEG file can only be lossless if it doesn’t have any partial blocks, i.e. if the dimensions are divisible by 16 (or 8, for some images); otherwise the partial blocks may be cropped, because they can only be on two of the four sides of a JPEG image; else the partial blocks are cropped.

The tag is supported by, e.g.:
* MediaWiki (it generates thumbnails rotated)
* digiKam (there is an option to set Orientation after rotating an image)
* Geeqie (rotates for displaying)
* Nautilus
* Eye of GNOME
* Thunar
* exiftran (according to the man page)