Comment by gavinray
Maybe I'm jaded, but I fail to see how a bespoke file format is a better solution than bundling a normal image and a JSON/XML document containing metadata that adheres to a defined specification.
It feels like creating a custom format with backwards PNG compatibility and using steganography to cram metadata inside is an inefficient and over-engineered alternative to a .tar.gz with "image.png" and "metadata.json"
That's fair and how it's traditionally done but the entire idea of this was to have everything you need on the image itself and reduce the complexity and extra files, no risk of losing the JSON, mismatching versions, or needing extra packaging steps.
I'm working on redundancy and error correction to make it better!