CutBox/bin/make_icon_pngs

#!/bin/sh
# -*- mode: sh -*-
if [ $# == 0 ]; then
  echo "$0 {appiconset} {master.png}"
  exit 1
fi

appiconset="${1}"
contents_json="${appiconset}/Contents.json"
cutbox_icon="${2}"

# Contents.json filenames are expected to be in the format {size}.png
# e.g. 128.png or anything with size as the first number in the filename
# 128-cutbox.png, 64icon_image.png, 512filename_anything etc.

jq '.images | .[] | .filename' $contents_json \
  | uniq \
  | tr -d '"' \
  | \
  while read file; do
    size=$(sed -E 's/^"([0-9]+).*/\1/' <<< "$file")
    # Any sips compatible input image
    sips -Z $size "$cutbox_icon" --out "$file"
    # We will replace the current images with the new ones (no undo)
    mv -v "$file" "$appiconset"
  done