public static void deduplicateImageList(final Collection<Image> list) {
        final Set<String> urls = new HashSet<>();
        final Iterator<Image> it = list.iterator();
        while (it.hasNext()) {
            final Image img = it.next();
            final String url = ImageUtils.imageUrlForSpoilerCompare(img.getUrl());
            if (urls.contains(url)) {
                it.remove();
            }
            urls.add(url);
        }
    }
Add images present in the HTML description to the existing collection.

@param htmlText the HTML description to be parsed, can be repeated
main/src/main/java/cgeo/geocaching/utils/ImageUtils.java