docs: public static void extract( DMatrix src,
                                  int srcY0, int srcY1,
                                  int srcX0, int srcX1,
                                  DMatrix dst ) {
          ((ReshapeMatrix)dst).reshape(srcY1-srcY0,srcX1-srcX0);
          extract(src,srcY0,srcY1,srcX0,srcX1,dst,0,0);
      }