A similar question was asked recently on Reddit. If you rotate the image, (Image>Transform),
However...
This holds for an image rotated with Image>Transform. This is not for an image where the view has been rotated with View>Flip & rotate, which, as its name implies, is just a presentation thing and doesn't really change the image.
- Gimp really rotates the pixels
- It also deletes the EXIF rotation flag in the image metadata
- From then on the image is saved without that flag (even if EXIF are exported), so the image should be displayed with the "natural" orientation (which is the one that was show in Gimp).
However...
This holds for an image rotated with Image>Transform. This is not for an image where the view has been rotated with View>Flip & rotate, which, as its name implies, is just a presentation thing and doesn't really change the image.