boost/gil/position_iterator.hpp

   1 //
   2 // Copyright 2005-2007 Adobe Systems Incorporated
   3 //
   4 // Distributed under the Boost Software License, Version 1.0
   5 // See accompanying file LICENSE_1_0.txt or copy at
   6 // http://www.boost.org/LICENSE_1_0.txt
   7 //
   8 #ifndef BOOST_GIL_POSITION_ITERATOR_HPP
   9 #define BOOST_GIL_POSITION_ITERATOR_HPP
  10
  11 #include <boost/gil/locator.hpp>
  12
  13 #include <boost/iterator/iterator_facade.hpp>
  14
  15 #include <type_traits>
  16
  17 namespace boost { namespace gil {
  18
  19 /// \defgroup PixelIteratorModelVirtual position_iterator
  20 /// \ingroup PixelIteratorModel
  21 /// \brief An iterator that remembers its current X,Y position and invokes a function object with it upon dereferencing.
  22 /// Models PixelIteratorConcept, PixelBasedConcept, HasDynamicXStepTypeConcept. Used to create virtual image views.
  23
  24 /// \brief An iterator that remembers its current X,Y position and invokes a function object with it upon dereferencing.
  25 /// Used to create virtual image views.
  26 /// Models: StepIteratorConcept, PixelIteratorConcept, PixelBasedConcept, HasDynamicXStepTypeConcept
  27 /// \ingroup PixelIteratorModelVirtual PixelBasedModel
  28 /// \tparam Deref A function object that given a point returns a pixel reference. Models PixelDereferenceAdaptorConcept
  29 /// \tparam Dim Dimension to advance along
  30 template <typename Deref, int Dim>
  31 struct position_iterator : public iterator_facade<position_iterator<Deref,Dim>,
  32                                                   typename Deref::value_type,
  33                                                   std::random_access_iterator_tag,
  34                                                   typename Deref::reference,
  35                                                   typename Deref::argument_type::template axis<Dim>::coord_t> {
  36     using parent_t = iterator_facade<position_iterator<Deref,Dim>,
  37                             typename Deref::value_type,
  38                             std::random_access_iterator_tag,
  39                             typename Deref::reference,
  40                             typename Deref::argument_type::template axis<Dim>::coord_t>;
  41     using difference_type = typename parent_t::difference_type;
  42     using reference = typename parent_t::reference;
  43     using point_t = typename Deref::argument_type;
  44
  45     position_iterator() {}
  46     position_iterator(const point_t& p, const point_t& step, const Deref& d) : _p(p), _step(step), _d(d) {}
  47
  48     position_iterator(const position_iterator& p) : _p(p._p), _step(p._step), _d(p._d) {}
  49     template <typename D> position_iterator(const position_iterator<D,Dim>& p) : _p(p._p), _step(p._step), _d(p._d) {}
  50     position_iterator& operator=(const position_iterator& p) { _p=p._p; _d=p._d; _step=p._step; return *this; }
  51
  52     const point_t&   pos()      const { return _p; }
  53     const point_t&   step()     const { return _step; }
  54     const Deref&     deref_fn() const { return _d; }
  55
  56     void set_step(difference_type s) { _step[Dim]=s; }
  57     /// For some reason operator[] provided by iterator_adaptor returns a custom class that is convertible to reference
  58     /// We require our own reference because it is registered in iterator_traits
  59     reference operator[](difference_type d) const { point_t p=_p; p[Dim]+=d*_step[Dim]; return _d(p); }
  60
  61 private:
  62     point_t _p, _step;
  63     Deref   _d;
  64
  65     template <typename DE, int DI> friend struct position_iterator;
  66     friend class boost::iterator_core_access;
  67     reference dereference()     const { return _d(_p); }
  68     void increment()                  { _p[Dim]+=_step[Dim]; }
  69     void decrement()                  { _p[Dim]-=_step[Dim]; }
  70     void advance(difference_type d)   { _p[Dim]+=d*_step[Dim]; }
  71
  72     difference_type distance_to(const position_iterator& it) const { return (it._p[Dim]-_p[Dim])/_step[Dim]; }
  73     bool equal(const position_iterator& it) const { return _p==it._p; }
  74 };
  75
  76 template <typename Deref,int Dim>
  77 struct const_iterator_type<position_iterator<Deref,Dim> > {
  78     using type = position_iterator<typename Deref::const_t,Dim>;
  79 };
  80
  81 template <typename Deref, int Dim>
  82 struct iterator_is_mutable<position_iterator<Deref, Dim>>
  83     : std::integral_constant<bool, Deref::is_mutable>
  84 {
  85 };
  86
  87 /////////////////////////////
  88 //  PixelBasedConcept
  89 /////////////////////////////
  90
  91 template <typename Deref,int Dim>
  92 struct color_space_type<position_iterator<Deref,Dim> > : public color_space_type<typename Deref::value_type> {};
  93
  94 template <typename Deref,int Dim>
  95 struct channel_mapping_type<position_iterator<Deref,Dim> > : public channel_mapping_type<typename Deref::value_type> {};
  96
  97 template <typename Deref,int Dim>
  98 struct is_planar<position_iterator<Deref, Dim>> : std::false_type {};
  99
 100 template <typename Deref,int Dim>
 101 struct channel_type<position_iterator<Deref,Dim> > : public channel_type<typename Deref::value_type> {};
 102
 103 /////////////////////////////
 104 //  HasDynamicXStepTypeConcept
 105 /////////////////////////////
 106
 107 template <typename Deref,int Dim>
 108 struct dynamic_x_step_type<position_iterator<Deref,Dim> > {
 109     using type = position_iterator<Deref,Dim>;
 110 };
 111
 112 } }  // namespace boost::gil
 113
 114 #endif