This script will generate all the images Xcode currently requires of your app for submission to the App Store(s), just replace SourceIcon1024.png with a nice big 1024 x 1024 source image of your icon and run the command below.
Now creates icons for Mac and Watch apps
./IconGenerator.sh SourceIcon1024.pngIf there are any missing images just let me know and I will add them.
sips -- scriptable image processing system