Given an input image as the single argument, creates all the files needed for a Universal iOS app (in the same directory, overwriting). Uses pngcrush to compress the images, but that's easily removed/commented out.

make_ios_icons.sh

#!/bin/bash

function make_icon {
    sips -s format png -Z $3 "$1" --out "$2"
    pngcrush -ow -q "$2"
}

echo "Using $1 as the base image."

echo "** App Store: iTunesArtwork **"
echo "Creating a 512px version..."
make_icon $1 iTunesArtwork.png 512
echo "Creating a 1024px version..."
make_icon $1 [email protected] 1024

echo "** iPhone: Icon **"
echo "Creating a 57px version..."
make_icon "$1" Icon.png 57
echo "Creating a 114px version..."
make_icon "$1" [email protected] 114

echo "** iPad: Icon-72 **"
echo "Creating a 72px version..."
make_icon "$1" Icon-72.png 72
echo "Creating a 144px version..."
make_icon "$1" [email protected] 144

echo "** iPhone Settings: Icon-Small **"
echo "Creating a 29px version..."
make_icon "$1" Icon-Small.png 29
echo "Creating a 58px version..."
make_icon "$1" [email protected] 58

echo "** iPad Settings: Icon-Small-50 **"
echo "Creating a 50px version..."
make_icon "$1" Icon-Small-50.png 50
echo "Creating a 100px version..."
make_icon "$1" [email protected] 100