code: public static List<String> getDistinctImageUrls(String htmlContent) {
  		Document doc = Jsoup.parse(htmlContent);
  		Elements els = doc.select(IMG_SELECTOR);
  		List<String> images = new ArrayList<>(els.size());
  		for (Element e : els) {
  			String path = e.attr(SRC_ATTR);
  			if (!images.contains(path)) {
  				images.add(path);
  			}
  		}
  		return images;
  	}
docs: Finds all image inclusions (looks for <code>img</code> tags). Returns
  only the path or URL to the image. If the several images have the same
  path, the path is present in the list only one time.
  
  @param htmlContent
  the html content that may contain image files
  @return the list of found images (paths only) or empty if nothing found