code: 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);
      }
docs: Extract where the destination is reshaped to match the extracted region
  @param src The original matrix which is to be copied.  Not modified.
  @param srcX0 Start column.
  @param srcX1 Stop column+1.
  @param srcY0 Start row.
  @param srcY1 Stop row+1.
  @param dst Where the submatrix are stored.  Modified.