image-annotator | Javascript tools to annotate images | Computer Vision library

For local files you need to load the file content, encode it, and put the encoded image content under the content key. For details, see here. The information about base64 encoding is linked on that page as well.

Your code can be updated as follows:

You really want to do this on the server side via something like Google Cloud Functions (see my example here).

Client side will require that your API key have sufficient permission to access the photos, which will basically make the private photos public (because once the API key has permission to read them, what's to stop a malicious client from doing so?).