code: function OpenMXL_GarbageCollector() {
  
  		if ( (count($this->IdxToCheck)==0) && (count($this->OtbsSheetSlidesDelete)==0) ) return;
  
  		// Key for Pictures
  		$pic_path = $this->ExtInfo['pic_path'];
  		$pic_path_len = strlen($pic_path);
  
  		// Key for Rels
  		$rels_ext = '.rels';
  		$rels_ext_len = strlen($rels_ext);
  
  		// List all Pictures and Rels files
  		$pictures = array();
  		$rels = array();
  		foreach ($this->CdFileLst as $idx=>$f) {
  			$n = $f['v_name'];
  			if (substr($n, 0, $pic_path_len)==$pic_path) {
  				$short = basename($pic_path).'/'.basename($n);
  				$pictures[] = array('name'=>$n, 'idx'=>$idx, 'nbr'=>0, 'short'=>$short);
  			} elseif (substr($n, -$rels_ext_len)==$rels_ext) {
  				if ($this->FileGetState($idx)!='d') $rels[$n] = $idx;
  			}
  		}
  
  		// Read contents or Rels files
  		foreach ($rels as $n=>$idx) {
  			$txt = $this->TbsStoreGet($idx, 'GarbageCollector');
  			foreach ($pictures as $i=>$info) {
  				if (strpos($txt, $info['short'].'"')!==false) $pictures[$i]['nbr']++;
  			}
  		}
  
  		// Delete unused Picture files
  		foreach ($pictures as $info) {
  			if ($info['nbr']==0) $this->FileReplace($info['idx'], false);
  		}
  
  		
  	}
docs: Delete unreferenced images