Which image optimization does Google Pagespeed use?

I try to optimize my site and check it with Google Pagespeed.

But whatever I try to reduce the size of my images doesn’t come near the results which Pagespeed gives me. They luckily offer these optimized contents for download, but none of the techniques they recommend nor any other tool like tinypng or imageoptim can produce similar results to Google Pagespeed.

Which tool can I use (on Mac) to get these great optimized images?