makeicns

#!/bin/bash

readonly program="$(basename "${0}")"

function get_output_path {
  readonly local ext='icns'
  readonly local input_path="${1}"
  local output_path="${2}"

  if [[ -n "${output_path}" ]]; then
    [[ "${output_path##*.}" == "${ext}" ]] && echo "${output_path}" || echo "${output_path}.${ext}"
  else
    output_path="${input_path%.*}.${ext}"

    while [[ -e "${output_path}" ]]; do
      output_path="${output_path%.*}_$(date -u +'%Y.%m.%d.%H%M%S').${ext}"
    done

    echo "${output_path}"
  fi
}

function usage {
  echo "
    Make an icns file from a png.

    Usage:
      ${program} [options] <file>

    Options:
      -o, --output-file <file>   File to output to. Default is saving next to the input file with same name.
      -h, --help                 Show this message.
  " | sed -E 's/ {4}//'
}

# available flags
args=()
while [[ "${1}" ]]; do
  case "${1}" in
    -h | --help)
      usage
      exit 0
      ;;
    -o | --output-file)
      readonly given_output_path="${2}"
      shift
      ;;
    --)
      shift
      args+=("${@}")
      break
      ;;
    -*)
      syntax_error "unrecognized option: ${1}"
      ;;
    *)
      args+=("${1}")
      ;;
  esac
  shift
done
set -- "${args[@]}"

if [[ "${1}" =~ ^(-h|--help)$ ]]; then
  usage
  exit 0
fi

if [[ "${#}" -eq 0 ]]; then
  usage
  exit 1
fi

readonly input_file="${1}"
readonly output_file="$(get_output_path "${input_file}" "${given_output_path}")"
readonly iconset="$(mktemp -d)"

if [[ "$(mdls -raw -name 'kMDItemContentType' "${input_file}")" != 'public.png' ]]; then
  echo 'Image needs to be a png.' >&2
  exit 1
fi

for size in {16,32,64,128,256,512}; do
  sips --resampleHeightWidth "${size}" "${size}" "${input_file}" --out "${iconset}/icon_${size}x${size}.png" &> /dev/null
  sips --resampleHeightWidth "$((size * 2))" "$((size * 2))" "${input_file}" --out "${iconset}/icon_${size}x${size}@2x.png" &> /dev/null
done

mv "${iconset}" "${iconset}.iconset"
iconutil --convert icns "${iconset}.iconset" --output "${output_file}"