Converts an image (e.g. PNG) to an ICNS icon-file. Inspired by https://stackoverflow.com/a/20703594

make-icns.sh

#!/bin/sh -e

#########################################
# Usage: 
#########################################
# for each png file in the directory:
#       sh make-icns.sh
#########################################
# for a specific file:
#       sh make-icns.sh filename.ext
#########################################

trap somethingFailed ERR

function somethingFailed() {
  echo "Something has failed. The job has bot been completed."
  exit 1
}

if [ $# -eq 0 ]
  then
    echo "Running script for each PNG file in the current directory..."
    for f in *.png ; do sh $0 "$f" ; done
    exit;
fi

mkdir $1.iconset
sips -z 16 16     $1 --out $1.iconset/icon_16x16.png
sips -z 32 32     $1 --out $1.iconset/icon_16x16@2x.png
sips -z 32 32     $1 --out $1.iconset/icon_32x32.png
sips -z 64 64     $1 --out $1.iconset/icon_32x32@2x.png
sips -z 128 128   $1 --out $1.iconset/icon_128x128.png
sips -z 256 256   $1 --out $1.iconset/icon_128x128@2x.png
sips -z 256 256   $1 --out $1.iconset/icon_256x256.png
sips -z 512 512   $1 --out $1.iconset/icon_256x256@2x.png
sips -z 512 512   $1 --out $1.iconset/icon_512x512.png
cp $1 $1.iconset/icon_512x512@2x.png
iconutil -c icns $1.iconset
rm -R $1.iconset

echo "$1.icns is ready!\n"