public function addThumb($maxDim, $folder)
 {
     $thumb = new self();
     $thumb->setPath($this->getFolderPath());
     $thumb->setMaxDim($maxDim);
     $thumb->setFolder($folder);
     $this->thumbs[$folder] = $thumb;
 }
 private function deleteOld()
 {
     $old = new self('*');
     $old->setFolder($this->folder);
     $old->setName($this->oldName);
     return $old->delete();
 }