svoid ai_saveMarkedFace(BufferedImage img, Rect r) {
  File f = putImageInDirectory_jpeg(img, ai_markedFacesDir());
  setFileInfoField(f, "Faces", r != null ? 1 : 0);
  setFileInfoField(f, "Face position", structOrNull(r));
  infoBox("Marked face saved");
}