code: protected JSONObject toReponsiveImageSource(Media media, MediaFormat mediaFormat) {
      String url = buildDummyImageUrl(mediaFormat);
      try {
        JSONObject source = new JSONObject();
        source.put(MediaNameConstants.PROP_BREAKPOINT, mediaFormat.getProperties().get(MediaNameConstants.PROP_BREAKPOINT));
        source.put(ResponsiveImageMediaMarkupBuilder.PROP_SRC, url);
        return source;
      }
      catch (JSONException ex) {
        throw new RuntimeException("Error building JSON source.", ex);
      }
    }
docs: Build JSON metadata for one rendition as image source.
  @param media Media
  @param mediaFormat Media format
  @return JSON metadata