ImageOptim and iPhoto 

ImageOptim is a simple Mac app that bundles a few image optimization tools to reduce the file size of your images by 10–20%. Handy, but not a big deal, right?

I ran it against my 40GB iPhoto library (lots of people have even bigger libraries). There are 3 folders in your iPhoto Library that have images:

• Masters/Originals
• Thumbnails
• Previews

It took me about a day of crunching images (just moving back and forth to the computer dragging folders over into the application). I could have scripted it, but I was lazy and walking over to the computer every hour or so was easier.

When finished, it saved about 1.5GB of useless information from my library. That’s not a ton, but that’s basically “free” free space. It’s incremental, and the nice thing about how iPhoto stores your pictures is that you can grab a folder each month and drag it in, and it’ll take about an hour a month or so. It his, however, diminishing returns if you’re using something like an iPhone as a camera. It seems that images generated by the iPhone are already reasonably well optimized, only maybe saving 8–10%.

Anyway—if you’re looking to squeeze a little bit more space out of your disk (maybe you’ve got an SSD), you’ll probably find a free GB or two in optimizing your image collection.