subsample.hh

// Copyright (C) 2009 EPITA Research and Development Laboratory (LRDE)
//
// This file is part of Olena.
//
// Olena is free software: you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free
// Software Foundation, version 2 of the License.
//
// Olena is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Olena.  If not, see <http://www.gnu.org/licenses/>.
//
// As a special exception, you may use this file as part of a free
// software project without restriction.  Specifically, if other files
// instantiate templates or use macros or inline functions from this
// file, or you compile this file and link it with other files to produce
// an executable, this file does not by itself cause the resulting
// executable to be covered by the GNU General Public License.  This
// exception does not however invalidate any other reasons why the
// executable file might be covered by the GNU General Public License.

#ifndef MLN_WORLD_BINARY_2D_SUBSAMPLE_HH
# define MLN_WORLD_BINARY_2D_SUBSAMPLE_HH


# include <mln/core/image/image2d.hh>
# include <mln/core/alias/dpoint2d.hh>
# include <mln/data/convert.hh>
# include <mln/value/int_u8.hh>

namespace mln
{

  namespace world
  {

    namespace binary_2d
    {

      //
      image2d<value::int_u8>
      subsample(image2d<bool>& input, unsigned n);


# ifndef MLN_INCLUDE_ONLY

      image2d<value::int_u8>
      subsample(image2d<bool>& input, unsigned n)
      {
        trace::entering("world::binary_2d::subsample");

        mln_precondition(input.is_valid());

        using value::int_u8;

        if (n == 0)
        {
          image2d<value::int_u8>
            output = data::convert(int_u8(), input);

          trace::exiting("world::binary_2d::subsample");
          return output;
        }

        const bool** ptr = new const bool*[n];
        const unsigned nrows = input.nrows() / n;
        const unsigned ncols = input.ncols() / n;
        algebra::vec<2, unsigned int> vmin;
        algebra::vec<2, unsigned int> vmax;
        vmin[0] = 0;
        vmin[1] = 0;
        vmax[0] = nrows - 1;
        vmax[1] = ncols - 1;
        point2d pmin(vmin);
        point2d pmax(vmax);
        image2d<int_u8> output(box<point2d>(pmin, pmax));

        dpoint2d dp_row(1, 0);
        const unsigned delta_row = input.delta_index(dp_row);
        unsigned count = 0;

        for (unsigned row = 0; row < nrows; ++row)
        {
          ptr[0] = & input(point2d(n * row, 0));
          for (unsigned i = 1; i < n; ++i)
            ptr[i] = ptr[i - 1] + delta_row;
          for (unsigned col = 0; col < ncols; ++col)
          {
            count = 0;
            for (unsigned i = 0; i < n; ++i)
            {
              for (unsigned j = 0; j < n; ++j, ++(ptr[i]))
              {
                if (*(ptr[i]))
                  ++count;
              }
            }
            output(point2d(row, col)) = count * 255 / n / n;
          }
        }

        trace::exiting("world::binary_2d::subsample");
        return output;
      }

# endif // ! MLN_INCLUDE_ONLY

    } // end of namespace mln::world::binary_2d

  } // end of namspace mln::world

} // end of namespace mln

#endif // ! MLN_WORLD_BINARY_2D_SUBSAMPLE_HH