favicon.sh

#!/bin/bash
# Converts an image in a multi-resolution favicon
# Requires Imagemagick
# 
# @link https://gist.github.com/lavoiesl/a7ccb4affe869d0a0bca

if [[ "$#" != "2" ]]; then
    echo "Usage: $0 input.png output.ico" >&2
    exit 1
fi

input="$1"
output="$2"
sizes="16 32 64 128 256"
tmp_dir=$(mktemp -d /tmp/favicon.XXXXXXXXXX)
files=""

for size in $sizes; do
    file="${tmp_dir}/${size}.png"
    convert "${input}" -resize "${size}x${size}" -background transparent -colors 256 -flatten "${file}"
    files="${files} ${file}"
done

convert "${files}" "${output}"
rm -R "${tmp_dir}"