I mentioned elsewhere my preference for Photoshop’s results (among the other methods considered) when resizing a single “master” 1024×1024 icon to all the various sizes needed for iOS/Android devices. (That is, assuming you’re a shoe-string operation and don’t have an artist on-staff to produce 20+ unique icons, hand-optimized for each resolution.)
Here is a script that can help automate that process, There are other such scripts floating around out there if you search for them, the only thing different here is that it’s specifically for Corona use, using their file-naming, and supporting all (currently) known sizes for both iOS/Android. (and it ought to be clear from a brief look at the source where you’d modify it to add additional sizes if/when they become necessary)
Save it somewhere locally, then File-Scripts-Browse… to it.
It’ll ask for a single high-resolution 1024×1024 master and an output folder, then just wait while it works.
Tested on CS2 and CS6. (ought to work on any >= CS2)