Uploading images to ghost Admin-API

Have you considered using the official Ghost JavaScript SDK? With it, you don’t have to worry about content types, formData or blobs. It would be like this:

import GhostAdminAPI from '@tryghost/admin-api'

const token = 'SECRET';

const api = new GhostAdminAPI({
  url: 'http://localhost:2368',
  key: token,
  version: "v5.0",
});

const apiRes = await api.images.upload({file: imagePath});

console.log(apiRes);

It’s documented here: