sclass BWII_MultiPatternFinder implements Iterable<FoundImg> {
  new L<BWImage> patternImages;
  int scaleWidth = /*256*/100; // width to scale input image to
  
  transient BWIntegralImage ii;
  transient IBWImage scaled;
  transient BWImage pattern;
  transient FoundImg found;

  *() {}
  *(L<BWImage> *patternImages, BWIntegralImage *ii) {}
  
  // only call once
  public Iterator<FoundImg> iterator() {
    ret nonNullIterator(mapI(patternImages, func(BWImage pat) {
      pattern = pat;
      FoundImg lastFound = found;
      if (scaled == null || scaled.getWidth() != scaleWidth)
        scaled = virtualScaledIntegralImageBW(ii, scaleWidth);
      FoundImg found2 = bwImageSearch_best_virtualBig(scaled, pat, found == null ? 0f : found.sim);
      if (found2 != null)
        ret found = found2;
      null;
    }));
  }
}