How to convert all photos in iPhoto library to no bigger than 1920x1920 resolution? My wife has a MASSIVE iPhoto library -- thousands of snapshots of her cat and food and flowers, vacation photos, and so on, all taken at the highest resolution on her digital camera (up to 12 Megapixels).

The library is taking up tonnes of space and it's bogging down iPhoto and her old iMac.

She only ever uses these photos for Facebook and things like that -- maybe some of them might get printed as 5"x7" prints for a photo album or something.

So I'm thinking it would be nice to reduce all of the images down to a max size of 1920 pixels (height or width, depending on landscape or portrait orientation).

Is there an easy way to reduce the size of all photos in the iPhoto library?

I was thinking of doing a massive export of all photos to a folder on an external drive with those max dimensions, but my concern is that I would lose all the iPhoto album organization.

Any thoughts?
Because these digital images represent irreplaceable data, and exporting in smaller resolutions in essence deletes some data, I'd move these images to an external HD to keep them in their original sizes.

For data-dense backups, inexpensive external dual-layer Blueray burners can store 50GB per disc.