in our use case we sometime need to rotate pictures after the files have been associated using Dropbox plugin.
Currently, we download the picture, rotate it locally and upload the new version but I think it could be interesting to allow rotation in omeka interface. Imagemagick needs to be installed on the server so it should be easy to allow rotation (convert -rotate 90 XXXX.jpg).
Do you think it should be integrated in omeka core or that I should go for a plugin ?
It sounds like a good idea for a plugin, maybe.
One thing to keep in mind: Omeka, as it works now, doesn't alter the original file with ImageMagick. I'm not sure whether your idea is to just rotate the thumbnails and other derivatives, or to rotate the original before it's added.
Just chiming in here to second that this would be a great feature, plugin or otherwise!
We've also been working with a giant batch of photos (that we batch-uploaded via a CSV import), and a large chunk of the images have required us (staff and volunteers) to rotate them locally (usually via Pixlr or Photoshop), which can make us cry when we come across particularly large stretches of photos needing rotation.
I've built a plugin that does the job, it's available on github if somebody is interested : https://github.com/symac/plugin-RotatePicture
There seems to be some bugs (thumbnail not refreshing immediatly for example) but I think that it works enough to be distrbuted.