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sauvola_functor.hh
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26 
27 #ifndef SCRIBO_BINARIZATION_INTERNAL_SAUVOLA_FUNCTOR_HH
28 # define SCRIBO_BINARIZATION_INTERNAL_SAUVOLA_FUNCTOR_HH
29 
33 
34 # include <mln/core/image/image2d.hh>
35 # include <mln/core/alias/neighb2d.hh>
36 # include <mln/extension/fill.hh>
37 
38 # include <scribo/binarization/internal/sauvola_formula.hh>
39 
40 # ifdef SCRIBO_LOCAL_THRESHOLD_DEBUG
41 # include <scribo/binarization/internal/local_threshold_debug.hh>
42 # endif // ! SCRIBO_LOCAL_THRESHOLD_DEBUG
43 
44 
45 namespace scribo
46 {
47 
48  namespace binarization
49  {
50 
51  namespace internal
52  {
53 
54  using namespace mln;
55 
56 
57  template <typename I>
59  {
60  // Moves in input and output images are made using "step"
61  // pixels. It corresponds to the scale ratio between the input
62  // image and the integral image used to give the statistics
63  // values.
64  enum { step = 3 };
65 
66  sauvola_functor(const Image<I>& input, double K, double R);
67 
68  void init();
69 
70  // Run every 4 pixels.
71  void exec(double mean, double stddev);
72 
73  void end_of_row(int);
74 
75  void finalize();
76 
77 
78  const I input;
79  mln_ch_value(I,bool) output;
80 
81  const mln_value(I)* pi;
82  bool* po;
83 
84  double K_;
85  double R_;
86 
88 
89  unsigned next_line3;
90  unsigned offset1;
91  unsigned offset2;
92  };
93 
94 #ifndef MLN_INCLUDE_ONLY
95 
96  template <typename I>
98  double K, double R)
99  : input(exact(input_)),
100  pi(&input(input.domain().pmin())),
101  K_(K),
102  R_(R)
103  {
104  mln_precondition(exact(input).is_valid());
105  mln_precondition(K > 0.);
106  mln_precondition(R > 0.);
107  }
108 
109 
110  template <typename I>
111  void
112  sauvola_functor<I>::init()
113  {
114  // This initialization MUST be done here since input image
115  // borders may have changed!
116 
117  // Since we iterate from a smaller image in the largest ones
118  // and image at scale 1 does not always have a size which can
119  // be divided by 3, some sites in the border may not be
120  // processed and we must skip them.
121  int more_offset = - (3 - input.ncols() % 3);
122  if (more_offset == - 3)
123  more_offset = 0; // No offset needed.
124 
125  next_line3 = input.delta_offset(dpoint2d(+2,0))
126  + 2 * input.border() + more_offset;
127 
128  offset1 = input.delta_offset(dpoint2d(+1,0));
129  offset2 = input.delta_offset(dpoint2d(+2,0));
130 
131  initialize(output, input);
132  po = &output(output.domain().pmin());
133  }
134 
135 
136  template <typename I>
137  void
138  sauvola_functor<I>::exec(double mean, double stddev)
139  {
140  mln_assertion(input.border() == output.border());
141 
142  double th = formula_(mean, stddev, K_, R_);
143 
144  for (int i = 0; i < step; ++i, ++po, ++pi)
145  {
146  *po = (*pi <= th);
147  *(po + offset1) = (*(pi + offset1) <= th);
148  *(po + offset2) = (*(pi + offset2) <= th);
149  }
150 
151 # ifdef SCRIBO_LOCAL_THRESHOLD_DEBUG
152  // Store local mean
153  unsigned index = pi - input.buffer();
154 
155  debug_mean.element(index) = mean * mean_debug_factor;
156  debug_stddev.element(index) = stddev * stddev_debug_factor;
157  debug_threshold.element(index) = th;
158 
159  double alpha = K_ * (1 - stddev / R_);
160  debug_alpham.element(index) = alpha * mean * alpham_debug_factor;
161  debug_alphacond.element(index) = (stddev < (alpha * mean / 2.));
162 # endif // ! SCRIBO_LOCAL_THRESHOLD_DEBUG
163 
164  }
165 
166  template <typename I>
167  void
168  sauvola_functor<I>::end_of_row(int)
169  {
170  po += next_line3;
171  pi += next_line3;
172  }
173 
174  template <typename I>
175  void
176  sauvola_functor<I>::finalize()
177  {
178  }
179 
180 #endif // ! MLN_INCLUDE_ONLY
181 
182  } // end of namespace scribo::binarization::internal
183 
184  } // end of namespace scribo::binarization
185 
186 } // end of namespace scribo
187 
188 #endif // SCRIBO_BINARIZATION_INTERNAL_SAUVOLA_FUNCTOR_HH