code: public void addFilter(String filter) {
  
          if (CmsStringUtil.isNotEmpty(filter)) {
              filter = filter.trim().toLowerCase();
              if (FILTERS.contains(filter)) {
                  m_filters.add(filter);
              }
          }
      }
docs: Adds a filter name to the list of filters that should be applied to the image.<p>
  
  @param filter the filter name to add