Emotion API and POST and HTTP requests library

Hi all.

I have tried to resolve this to no avail. I just don't know what I'm doing wrong. I really hope someone out there can point me in the right direction. Apologies if my use of terminology is occasionally bogus below - network stuff is not my usual bag.

Basically, I'm trying to use the Microsoft Emotion API in Processing: https://dev.projectoxford.ai/docs/services/5639d931ca73072154c1ce89/operations/563b31ea778daf121cc3a5fa It requires API key authentication and HTTP headers as a POST request. I found the HTTP requests library (by Shiffman et al) which apparently takes the pain away (heh) and built a test example below:

import http.requests.*;
PostRequest post;

void setup() {
  size(400, 400);
  makeRequest();
  //println("Reponse Content: " + post.getContent());
  //println("Reponse Content-Length Header: " + post.getHeader("Content-Length"));
  JSONObject response = parseJSONObject(post.getContent());
  println(response);
}

void makeRequest() {
  post = new PostRequest("https://" + "westus.api.cognitive.microsoft.com/emotion/v1.0/recognize");
  post.addHeader("Content-Type", "application/json");
  post.addHeader("Ocp-Apim-Subscription-Key", MyAPIkeyGoesHere);
  post.addData("url", "http://" + "www.boro.gr/contentfiles_2016/psyxologia/thymos/axaaamm.jpg");
  post.send();
}

What I should get back is a JSON file that looks like this:

  {
    "faceRectangle": {
      "height": 216,
      "left": 225,
      "top": 90,
      "width": 216
    },
    "scores": {
      "anger": 9.38430444E-11,
      "contempt": 3.36862873E-12,
      "disgust": 4.649468E-11,
      "fear": 1.913897E-11,
      "happiness": 1.0,
      "neutral": 7.306441E-11,
      "sadness": 1.65613755E-11,
      "surprise": 2.97461256E-09
    }
  }

... but what I get is this:

{"error": {
  "code": "BadBody",
  "message": "JSON parsing error."
}}

Anybody know what's going on? Also, if I was wanting to upload an image locally, how would I do that? Apologies for lameness, but am very grateful for any help. Thanks.

Kind regards, Paul.