It can be hidden in the URL of the file 🤔 I think. But I am not the best person to respond to this tho lol
Discussion
Don’t know details, but appears this particular method is based on changing a pixel in the original. See this note:
You and nostr:nprofile1qqsd9pqnwyshrse7z975h5ynptq9ktz3kv8txqs7lr20zgelqtys52cpz3mhxue69uhhyetvv9ujuerpd46hxtnfduqnxamnwvaz7tmwwa3juurjd9kkzmpwdejhgtesd93x5dt8dfhxu7th0p6nvemyxuuk76e40pekgvt3xv6hsdq3qlfgu offered a good springboard to research it further. Much appreach!