It says in the README it leverages Dive. Basically it's a visualization for Dive's JSON output, which I'd very much prefer to exist as exactly that -- something I can pipe Dive's JSON into. No need to wrap Dive for that.

Dive doesn't have a JSON output, I had to use the internal API to do it.

What do you mean? It's literally there:

  $ dive -j /dev/stdout alpine:edge
  Image Source: docker://alpine:edge
  Fetching image... (this can take a while for large images)
  Analyzing image...
  Exporting image to '/dev/stdout'...
  {
    "layer": [
      {
        "index": 0,
        "id": "blobs",
        "digestId": "sha256:8980900bae6f916f9dc1158ed71ee72566d7ad3f47f63fe19ba3ab7a4ef1a432",
        "sizeBytes": 7738376,
        "command": "#(nop) ADD file:5ba6edac87fa0feb475d0ddae7299210c6f2b69714784771ca86fcb6407ae8fc in / "
      }
    ],
    "image": {
      "sizeBytes": 7738376,
      "inefficientBytes": 0,
      "efficiencyScore": 1,
      "fileReference": []
    }
  }