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An Image Processing Platform
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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 
37 
38 # include <mln/core/image/image2d.hh>
39 # include <mln/core/alias/dpoint2d.hh>
40 # include <mln/data/convert.hh>
41 # include <mln/value/int_u8.hh>
42 
43 
44 namespace mln
45 {
46 
47  namespace world
48  {
49 
50  namespace binary_2d
51  {
52 
59  image2d<value::int_u8>
60  subsample(const image2d<bool>& input, unsigned n);
61 
62 
63 # ifndef MLN_INCLUDE_ONLY
64 
65  inline
66  image2d<value::int_u8>
67  subsample(const image2d<bool>& input, unsigned n)
68  {
69  mln_trace("world::binary_2d::subsample");
70 
71  mln_precondition(input.is_valid());
72 
73  using value::int_u8;
74 
75  if (n == 0)
76  return data::convert(int_u8(), input);
77 
78  const bool** ptr = new const bool*[n];
79  const unsigned nrows = input.nrows() / n;
80  const unsigned ncols = input.ncols() / n;
81  image2d<int_u8> output(nrows, ncols);
82 
83  const unsigned delta_row = input.delta_offset(down);
84 
85  for (unsigned row = 0; row < nrows; ++row)
86  {
87  ptr[0] = & input(point2d(n * row, 0));
88  for (unsigned i = 1; i < n; ++i)
89  ptr[i] = ptr[i - 1] + delta_row;
90  for (unsigned col = 0; col < ncols; ++col)
91  {
92  unsigned count = 0;
93  for (unsigned i = 0; i < n; ++i)
94  for (unsigned j = 0; j < n; ++j, ++(ptr[i]))
95  if (*(ptr[i]))
96  ++count;
97  output(point2d(row, col)) = count * mln_max(int_u8) / n / n;
98  }
99  }
100 
101  delete[] ptr;
102 
103  return output;
104  }
105 
106 # endif // ! MLN_INCLUDE_ONLY
107 
108  } // end of namespace mln::world::binary_2d
109 
110  } // end of namspace mln::world
111 
112 } // end of namespace mln
113 
114 #endif // ! MLN_WORLD_BINARY_2D_SUBSAMPLE_HH