Respect EXIF orientation

[keeth]

Thor strips the EXIF metadata from the image, but ignores the EXIF orientation parameter, so images that are processed with Thor will look sideways if they have a orientation other than 1 (normal top-left orientation). It would be cool if Thor would either preserve EXIF metadata or perform a rotation to account for removing the orientation flag.

[rstecker]

Thor can make a composite image out of multiple images, so preserving the metadata doesn't really work

Performing the rotation might be possible, but the behavior in terms of changed aspect ratios is not-great... is it centered? left aligned?

Would an explicate filter make sense? Something like honor_exif_orientation()?

[mlrsmith]

I think it should just rotate it on load. It'd be transparent then to the rest of thor (and to the consuming application) if the source image was e.g. a 400x200 image, or a 200x400 image that got rotated - so there's no (additional) problems with aspect ratios.

[keeth]

Yeah I agree that preserving EXIF doesn't make sense. Thanks for pointing that out.

I think either of the other options could work - either rotate automatically/transparently or provide an explicit filter.

ImageMagick does the latter - an explicit, optional filter called auto-orient

I think I would lean towards the former (do it automatically and transparently). Image editing/display programs that are EXIF-orientation aware seem to generally do this - I can't think of a situation where you'd want your portrait image to be shown sideways.

Thanks!