I made an app that lets you write memos on images, like the tagging feature on Instagram.
It's handy for labeling parts during anatomy or observation experiments, or marking good spots on a map when traveling.
Display Formats
Pop-up

Memos appear in speech bubbles.
There are two types - one that always shows memos, and one that only shows a selected memo.
Line-connected

Memos are displayed connected by a line, like a scouter from Dragon Ball.
This format is easier to read when there are lots of memos.
Install
You can install it here! Give it a try!
