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subsample.hh
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26 
27 #ifndef MLN_WORLD_BINARY_2D_SUBSAMPLE_HH
28 # define MLN_WORLD_BINARY_2D_SUBSAMPLE_HH
29 
36 
37 # include <mln/core/image/image2d.hh>
38 # include <mln/core/alias/dpoint2d.hh>
39 # include <mln/data/convert.hh>
40 # include <mln/value/int_u8.hh>
41 
42 namespace mln
43 {
44 
45  namespace world
46  {
47 
48  namespace binary_2d
49  {
50 
57  //
58  image2d<value::int_u8>
59  subsample(image2d<bool>& input, unsigned n);
60 
61 
62 # ifndef MLN_INCLUDE_ONLY
63 
64  inline
65  image2d<value::int_u8>
66  subsample(image2d<bool>& input, unsigned n)
67  {
68  trace::entering("world::binary_2d::subsample");
69 
70  mln_precondition(input.is_valid());
71 
72  using value::int_u8;
73 
74  if (n == 0)
75  {
76  image2d<value::int_u8>
77  output = data::convert(int_u8(), input);
78 
79  trace::exiting("world::binary_2d::subsample");
80  return output;
81  }
82 
83  const bool** ptr = new const bool*[n];
84  const unsigned nrows = input.nrows() / n;
85  const unsigned ncols = input.ncols() / n;
86  algebra::vec<2, unsigned int> vmin;
87  algebra::vec<2, unsigned int> vmax;
88  vmin[0] = 0;
89  vmin[1] = 0;
90  vmax[0] = nrows - 1;
91  vmax[1] = ncols - 1;
92  point2d pmin(vmin);
93  point2d pmax(vmax);
94  image2d<int_u8> output(box<point2d>(pmin, pmax));
95 
96  dpoint2d dp_row(1, 0);
97  const unsigned delta_row = input.delta_index(dp_row);
98  unsigned count = 0;
99 
100  for (unsigned row = 0; row < nrows; ++row)
101  {
102  ptr[0] = & input(point2d(n * row, 0));
103  for (unsigned i = 1; i < n; ++i)
104  ptr[i] = ptr[i - 1] + delta_row;
105  for (unsigned col = 0; col < ncols; ++col)
106  {
107  count = 0;
108  for (unsigned i = 0; i < n; ++i)
109  {
110  for (unsigned j = 0; j < n; ++j, ++(ptr[i]))
111  {
112  if (*(ptr[i]))
113  ++count;
114  }
115  }
116  output(point2d(row, col)) = count * 255 / n / n;
117  }
118  }
119 
120  trace::exiting("world::binary_2d::subsample");
121  return output;
122  }
123 
124 # endif // ! MLN_INCLUDE_ONLY
125 
126  } // end of namespace mln::world::binary_2d
127 
128  } // end of namspace mln::world
129 
130 } // end of namespace mln
131 
132 #endif // ! MLN_WORLD_BINARY_2D_SUBSAMPLE_HH