Mac OS X & Photoshop CS3 or CS4

Your operating system is Mac OS X. And you have Photoshop CS5 or newer

These are Universal binary plug-ins for Photoshop CS3 and CS4 and can be used on both PowerPC en Intel based Macs

MultiFill Macintosh CS3 (Free)

Flatten Macintosh CS3 (Free)

Flatten Pro Macintosh CS3