How does iPhoto handle rotating images? 'Revert to Original' Issue

Question

I use iPhoto for all my images, and need to get my head around how it stores images, particularly when edited. If I rotate a photo, for example from horizontal to landscape, then I think it stores the old version, and the new version. I can use the menu to 'Revert to Original' - which shows the unrotated image.
According to iPhoto, my library size is 24.8gb.
According to Finder, the library size is 34.2gb
I would like to reclaim this nearly 10gb back, as if I have rotated a photo, I do not need the original version! It would also be nice to change the iPhoto behaviour, so when you rotate an image, it does not create a new file.
I have heard of iPhoto diet, but that does not work reliably for newer versions.
I use iPhoto 7.1.4 (the latest) and any help or advice would be appreciated.

Answer 1

Welcome to the Apple Discussions. The best way to do what you want for future photos is to upload the photos from the camera to a folder on the desktop, rotate the file there before importing into iPhoto. There are 3rd party applications that can losslessly rotate image files. Also do not turn on the Auto-Rotate feature of your camera if it has one.
For those that are already in the library the only way to do what you want is to replace the original file with a copy of the edited file inside the library package and then do a revert to original on that file.
To facilitate replacing the original files with a copy of the edited (modified) files put all of the files you want to replace into one Event. That will put them all in one folder within the Originals folder and Modified folder. Then copy the contents of the Modified subfolder into the corresponding Originals subfolder.
You run a big risk of damaging the library if an error is made during the process. It's really not recommended. In other words *proceed at your own risk and make a backup of the library before proceeding*.
The reason the finder reports a larger library is that it is reporting the original, thumbnail and modified files as well as the database, cache and data files.
TIP: For insurance against the iPhoto database corruption that many users have experienced I recommend making a backup copy of the Library6.iPhoto (iPhoto.Library for iPhoto 5 and earlier) database file and keep it current. If problems crop up where iPhoto suddenly can't see any photos or thinks there are no photos in the library, replacing the working Library6.iPhoto file with the backup will often get the library back. By keeping it current I mean backup after each import and/or any serious editing or work on books, slideshows, calendars, cards, etc. That insures that if a problem pops up and you do need to replace the database file, you'll retain all those efforts. It doesn't take long to make the backup and it's good insurance.
I've created an Automator workflow application (requires Tiger or later), iPhoto dB File Backup, that will copy the selected Library6.iPhoto file from your iPhoto Library folder to the Pictures folder, replacing any previous version of it. It's compatible with iPhoto 6 and 7 libraries and Tiger and Leopard. Just put the application in the Dock and click on it whenever you want to backup the dB file. iPhoto does not have to be closed to run the application, just idle. You can download it at Toad's Cellar. Be sure to read the Read Me pdf file.
Note: There's now an Automator backup application for iPhoto 5 that will work with Tiger or Leopard.