docs: public static GrayU8 loadPGM_U8(InputStream inputStream , GrayU8 storage ) throws IOException {
  		DataInputStream in = new DataInputStream(inputStream);
  
  		readLine(in);
  		String line = readLine(in);
  		while( line.charAt(0) == '#')
  			line = readLine(in);
  		String s[] = line.split(" ");
  		int w = Integer.parseInt(s[0]);
  		int h = Integer.parseInt(s[1]);
  		readLine(in);
  
  		if( storage == null )
  			storage = new GrayU8(w,h);
  
  		read(in,storage.data,w*h);
  
  		return storage;
  	}