Changing background image periodically

Yeah, I didn't explain this very well: I keep most of my images inside iPhoto, including a bunch of backdrops (924 images, which Ive collected over the years).

They are all part of the same album, "Backdrops", in iPhoto. Now, albums in iPhoto do not correspond directly to a single folder on my drive, so its not a case of simply adding that folder (if only it were that easy!).

You used to be able to pick an iPhoto album on older versions of OS X and then tell it to pick a random image and change it periodically. This feature seems to have been changed and then removed entirely. Try this: in System Prefs -> Desktop & ScreenSaver, select an iPhoto album; you will note that the "Change picture" options at the bottom of the dialog box become grayed out - they are only available for "regular" folders, not iPhoto albums (even though albums are listed there).

Another thing I tried was selecting all my images in that album in iPhoto, then adding my iPhoto Selection folder to the list of folders. As you correctly pointed out, the selection appears to be "cached" and new images will not appear. But in my case, this didn't work at all, I see no thumbnails (maybe it chokes on 924 images? 🙂

And when you select the iPhoto album, you will note that the "Change Picture" options at the bottom become greyed-out and unavailable.

Used to be possible to use those in older versions of OS X.

In other words, copy all the files from that album into a single folder and use that instead? Hmmm... sure it do-able though Im wasting an additional 640Mb in doing that.

If I click *Choose Folder* and select *Home -> Pictures -> iPhoto Library*, I see no pictures after I click OK.

That's right, the options are grayed out if you select anything below the divider line. This was not the case on older releases of OS X.

Now, I did some experimenting with some interesting results: apparently if use the command-line and create a symbolic link to an image from another folder (which I created), I can then choose that folder and the symbolic links inside to the real image files work. (This has the added advantage that it uses practially zero disk space).

After some more digging around I realized that the *iPhoto Selection* folder works exactly this way.

After yet more digging I realized that the links I have in there right now have the wrong path (I upgraded machines, my username changed, but I copied my old iPhoto Library across to the new machine manually instead of using the migration assistant).

Now I just have to figure out how those links get created. Im assuming iPhoto on an older machine created those but doing *Select All* inside my Backdrops album doesn't appear to re-create them, so maybe newer versions of iPhoto work differently.

If there's no way in iPhoto to do it, there's probably a way to script this some way so I can manually re-generate those symbolic links by running a script.