nativefier/icon-scripts/convertToPng

#!/usr/bin/env bash

# USAGE

# ./convertToPng <input png or ico> <outfilename>.png
# Example
# ./convertToPng ~/sample.ico ~/Desktop/converted.png

set -e

type convert >/dev/null 2>&1 || { echo >&2 "Cannot find required ImageMagick 'convert' executable, please install it and make sure it is in your PATH"; exit 1; }
type identify >/dev/null 2>&1 || { echo >&2 "Cannot find required ImageMagick 'identify' executable, please install it and make sure it is in your PATH"; exit 1; }

# Parameters
SOURCE="$1"
DEST="$2"

# Check source and destination arguments
if [ -z "${SOURCE}" ]; then
	echo "No source image specified"
	exit 1
fi

if [ -z "${DEST}" ]; then
	echo "No destination specified"
	exit 1
fi

# File Infrastructure
NAME=$(basename "${SOURCE}")
BASE="${NAME%.*}"
TEMP_DIR="convert_temp"

function cleanUp() {
    rm -rf "${TEMP_DIR}"
}

trap cleanUp EXIT

mkdir -p "${TEMP_DIR}"

# check if .ico is a sequence
# pipe into cat so no exit code is given for grep if no matches are found
IS_ICO_SET="$(identify "${SOURCE}" | grep -e "\w\.ico\[0" | cat )"

convert "${SOURCE}" "${TEMP_DIR}/${BASE}.png"
if [ "${IS_ICO_SET}" ]; then
	# extract the largest(?) image from the set
    cp "${TEMP_DIR}/${BASE}-0.png" "${DEST}"
else
    cp "${TEMP_DIR}/${BASE}.png" "${DEST}"
fi

rm -rf "${TEMP_DIR}"

trap - EXIT
cleanUp