On iOS there seems to be about a billion different icon sizes, depending on if you’re on iOS 7 or iOS 6, on iPhone or iPad, or for search icons or whatever.

This is a script which I created to help automatically resize all the icons that are used.

if [ $# -gt 0 ]; then
    sips $1 -Z 29 --out icon-29.png
    sips $1 -Z 58 --out icon-29@2x.png
    sips $1 -Z 40 --out icon-40.png
    sips $1 -Z 80 --out icon-40@2x.png
    sips $1 -Z 50 --out icon-50.png
    sips $1 -Z 100 --out icon-50@2x.png
    sips $1 -Z 57 --out icon-57.png
    sips $1 -Z 114 --out icon-57@2x.png
    sips $1 -Z 60 --out icon-60.png
    sips $1 -Z 120 --out icon-60@2x.png
    sips $1 -Z 72 --out icon-72.png
    sips $1 -Z 144 --out icon-72@2x.png
    sips $1 -Z 76 --out icon-76.png
    sips $1 -Z 152 --out icon-76@2x.png
    echo "Done."
else
    echo "You must provide the name of an image file to process."
fi

To use, in the terminal execute this script with the name of the .png file to be resized, and this will generate all the different icon sizes used.