I'm using Adobe Photoshop Express on my iPad. I want to use it on my iMac as well to see things a little bigger and easily send via email and such while at home. Adobe Photoshop Express was free in the App store with In-App Purchases on the iPad. No app available on the iMac. how to I make it work on my iMac? Not interested in purchasing large products just yet.
PS Touch was a little more fully-featured vs. Photoshop Express. (I don't think Express could work with layers like Touch could, either.)
Note that PS Touch was discontinued whereas Express is still being supported. Photoshop Mix and the forthcoming "Project Rigel" are supposed to more or less fill in the gaps left behind by Touch.
I'm not sure if iOS apps could even be used on Mac OS. (My guess would be no.)