#!/bin/sh
#
# Builds .icns file from a single .png file
#

set -e

filename="${1%.*}"
mkdir "$filename".iconset
for i in 16 32 128 256 ; do
    n=$(( i * 2 ))
    sips -z $i $i "$1" --out "$filename".iconset/icon_${i}x${i}.png
    sips -z $n $n "$1" --out "$filename".iconset/icon_${i}x${i}@2x.png
    [[ $n -eq 512 ]] && \
    sips -z $n $n "$1" --out "$filename".iconset/icon_${n}x${n}.png
    (( i++ ))
done
cp "$1" "$filename".iconset/icon_512x512@2x.png
iconutil -c icns "$filename".iconset
rm -r "$filename".iconset