/* | |
Copyright 2005-2007 Adobe Systems Incorporated | |
Use, modification and distribution are subject to the Boost Software License, | |
Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at | |
http://www.boost.org/LICENSE_1_0.txt). | |
See http://opensource.adobe.com/gil for most recent version including documentation. | |
*/ | |
/*************************************************************************************************/ | |
#ifndef GIL_STEP_ITERATOR_H | |
#define GIL_STEP_ITERATOR_H | |
//////////////////////////////////////////////////////////////////////////////////////// | |
/// \file | |
/// \brief pixel step iterator | |
/// \author Lubomir Bourdev and Hailin Jin \n | |
/// Adobe Systems Incorporated | |
/// \date 2005-2007 \n Last updated on September 18, 2007 | |
/// | |
//////////////////////////////////////////////////////////////////////////////////////// | |
#include <cstddef> | |
#include <iterator> | |
#include <boost/iterator/iterator_facade.hpp> | |
#include "gil_config.hpp" | |
#include "utilities.hpp" | |
#include "pixel_iterator.hpp" | |
#include "pixel_iterator_adaptor.hpp" | |
namespace boost { namespace gil { | |
/// \defgroup PixelIteratorModelStepPtr step iterators | |
/// \ingroup PixelIteratorModel | |
/// \brief Iterators that allow for specifying the step between two adjacent values | |
namespace detail { | |
/// \ingroup PixelIteratorModelStepPtr | |
/// \brief An adaptor over an existing iterator that changes the step unit | |
/// | |
/// (i.e. distance(it,it+1)) by a given predicate. Instead of calling base's | |
/// operators ++, --, +=, -=, etc. the adaptor is using the passed policy object SFn | |
/// for advancing and for computing the distance between iterators. | |
template <typename Derived, // type of the derived class | |
typename Iterator, // Models Iterator | |
typename SFn> // A policy object that can compute the distance between two iterators of type Iterator | |
// and can advance an iterator of type Iterator a given number of Iterator's units | |
class step_iterator_adaptor : public iterator_adaptor<Derived, Iterator, use_default, use_default, use_default, typename SFn::difference_type> { | |
public: | |
typedef iterator_adaptor<Derived, Iterator, use_default, use_default, use_default, typename SFn::difference_type> parent_t; | |
typedef typename std::iterator_traits<Iterator>::difference_type base_difference_type; | |
typedef typename SFn::difference_type difference_type; | |
typedef typename std::iterator_traits<Iterator>::reference reference; | |
step_iterator_adaptor() {} | |
step_iterator_adaptor(const Iterator& it, SFn step_fn=SFn()) : parent_t(it), _step_fn(step_fn) {} | |
difference_type step() const { return _step_fn.step(); } | |
protected: | |
SFn _step_fn; | |
private: | |
friend class boost::iterator_core_access; | |
void increment() { _step_fn.advance(this->base_reference(),1); } | |
void decrement() { _step_fn.advance(this->base_reference(),-1); } | |
void advance(base_difference_type d) { _step_fn.advance(this->base_reference(),d); } | |
difference_type distance_to(const step_iterator_adaptor& it) const { return _step_fn.difference(this->base_reference(),it.base_reference()); } | |
}; | |
// although iterator_adaptor defines these, the default implementation computes distance and compares for zero. | |
// it is often faster to just apply the relation operator to the base | |
template <typename D,typename Iterator,typename SFn> inline | |
bool operator>(const step_iterator_adaptor<D,Iterator,SFn>& p1, const step_iterator_adaptor<D,Iterator,SFn>& p2) { | |
return p1.step()>0 ? p1.base()> p2.base() : p1.base()< p2.base(); | |
} | |
template <typename D,typename Iterator,typename SFn> inline | |
bool operator<(const step_iterator_adaptor<D,Iterator,SFn>& p1, const step_iterator_adaptor<D,Iterator,SFn>& p2) { | |
return p1.step()>0 ? p1.base()< p2.base() : p1.base()> p2.base(); | |
} | |
template <typename D,typename Iterator,typename SFn> inline | |
bool operator>=(const step_iterator_adaptor<D,Iterator,SFn>& p1, const step_iterator_adaptor<D,Iterator,SFn>& p2) { | |
return p1.step()>0 ? p1.base()>=p2.base() : p1.base()<=p2.base(); | |
} | |
template <typename D,typename Iterator,typename SFn> inline | |
bool operator<=(const step_iterator_adaptor<D,Iterator,SFn>& p1, const step_iterator_adaptor<D,Iterator,SFn>& p2) { | |
return p1.step()>0 ? p1.base()<=p2.base() : p1.base()>=p2.base(); | |
} | |
template <typename D,typename Iterator,typename SFn> inline | |
bool operator==(const step_iterator_adaptor<D,Iterator,SFn>& p1, const step_iterator_adaptor<D,Iterator,SFn>& p2) { | |
return p1.base()==p2.base(); | |
} | |
template <typename D,typename Iterator,typename SFn> inline | |
bool operator!=(const step_iterator_adaptor<D,Iterator,SFn>& p1, const step_iterator_adaptor<D,Iterator,SFn>& p2) { | |
return p1.base()!=p2.base(); | |
} | |
} // namespace detail | |
//////////////////////////////////////////////////////////////////////////////////////// | |
/// MEMORY-BASED STEP ITERATOR | |
//////////////////////////////////////////////////////////////////////////////////////// | |
/// \class memory_based_step_iterator | |
/// \ingroup PixelIteratorModelStepPtr PixelBasedModel | |
/// \brief Iterator with dynamically specified step in memory units (bytes or bits). Models StepIteratorConcept, IteratorAdaptorConcept, MemoryBasedIteratorConcept, PixelIteratorConcept, HasDynamicXStepTypeConcept | |
/// | |
/// A refinement of step_iterator_adaptor that uses a dynamic parameter for the step | |
/// which is specified in memory units, such as bytes or bits | |
/// | |
/// Pixel step iterators are used to provide iteration over non-adjacent pixels. | |
/// Common use is a vertical traversal, where the step is the row stride. | |
/// | |
/// Another application is as a sub-channel view. For example, a red intensity image over | |
/// interleaved RGB data would use a step iterator adaptor with step sizeof(channel_t)*3 | |
/// In the latter example the step size could be fixed at compile time for efficiency. | |
/// Compile-time fixed step can be implemented by providing a step function object that takes the step as a template | |
//////////////////////////////////////////////////////////////////////////////////////// | |
/// \ingroup PixelIteratorModelStepPtr | |
/// \brief function object that returns the memory unit distance between two iterators and advances a given iterator a given number of mem units (bytes or bits) | |
template <typename Iterator> | |
struct memunit_step_fn { | |
typedef std::ptrdiff_t difference_type; | |
memunit_step_fn(difference_type step=memunit_step(Iterator())) : _step(step) {} | |
difference_type difference(const Iterator& it1, const Iterator& it2) const { return memunit_distance(it1,it2)/_step; } | |
void advance(Iterator& it, difference_type d) const { memunit_advance(it,d*_step); } | |
difference_type step() const { return _step; } | |
void set_step(std::ptrdiff_t step) { _step=step; } | |
private: | |
GIL_CLASS_REQUIRE(Iterator, boost::gil, MemoryBasedIteratorConcept) | |
difference_type _step; | |
}; | |
template <typename Iterator> | |
class memory_based_step_iterator : public detail::step_iterator_adaptor<memory_based_step_iterator<Iterator>, | |
Iterator, | |
memunit_step_fn<Iterator> > { | |
GIL_CLASS_REQUIRE(Iterator, boost::gil, MemoryBasedIteratorConcept) | |
public: | |
typedef detail::step_iterator_adaptor<memory_based_step_iterator<Iterator>, | |
Iterator, | |
memunit_step_fn<Iterator> > parent_t; | |
typedef typename parent_t::reference reference; | |
typedef typename parent_t::difference_type difference_type; | |
typedef Iterator x_iterator; | |
memory_based_step_iterator() : parent_t(Iterator()) {} | |
memory_based_step_iterator(Iterator it, std::ptrdiff_t memunit_step) : parent_t(it, memunit_step_fn<Iterator>(memunit_step)) {} | |
template <typename I2> | |
memory_based_step_iterator(const memory_based_step_iterator<I2>& it) | |
: parent_t(it.base(), memunit_step_fn<Iterator>(it.step())) {} | |
/// For some reason operator[] provided by iterator_adaptor returns a custom class that is convertible to reference | |
/// We require our own reference because it is registered in iterator_traits | |
reference operator[](difference_type d) const { return *(*this+d); } | |
void set_step(std::ptrdiff_t memunit_step) { this->_step_fn.set_step(memunit_step); } | |
x_iterator& base() { return parent_t::base_reference(); } | |
x_iterator const& base() const { return parent_t::base_reference(); } | |
}; | |
template <typename Iterator> | |
struct const_iterator_type<memory_based_step_iterator<Iterator> > { | |
typedef memory_based_step_iterator<typename const_iterator_type<Iterator>::type> type; | |
}; | |
template <typename Iterator> | |
struct iterator_is_mutable<memory_based_step_iterator<Iterator> > : public iterator_is_mutable<Iterator> {}; | |
///////////////////////////// | |
// IteratorAdaptorConcept | |
///////////////////////////// | |
template <typename Iterator> | |
struct is_iterator_adaptor<memory_based_step_iterator<Iterator> > : public mpl::true_{}; | |
template <typename Iterator> | |
struct iterator_adaptor_get_base<memory_based_step_iterator<Iterator> > { | |
typedef Iterator type; | |
}; | |
template <typename Iterator, typename NewBaseIterator> | |
struct iterator_adaptor_rebind<memory_based_step_iterator<Iterator>,NewBaseIterator> { | |
typedef memory_based_step_iterator<NewBaseIterator> type; | |
}; | |
///////////////////////////// | |
// PixelBasedConcept | |
///////////////////////////// | |
template <typename Iterator> | |
struct color_space_type<memory_based_step_iterator<Iterator> > : public color_space_type<Iterator> {}; | |
template <typename Iterator> | |
struct channel_mapping_type<memory_based_step_iterator<Iterator> > : public channel_mapping_type<Iterator> {}; | |
template <typename Iterator> | |
struct is_planar<memory_based_step_iterator<Iterator> > : public is_planar<Iterator> {}; | |
template <typename Iterator> | |
struct channel_type<memory_based_step_iterator<Iterator> > : public channel_type<Iterator> {}; | |
///////////////////////////// | |
// MemoryBasedIteratorConcept | |
///////////////////////////// | |
template <typename Iterator> | |
struct byte_to_memunit<memory_based_step_iterator<Iterator> > : public byte_to_memunit<Iterator> {}; | |
template <typename Iterator> | |
inline std::ptrdiff_t memunit_step(const memory_based_step_iterator<Iterator>& p) { return p.step(); } | |
template <typename Iterator> | |
inline std::ptrdiff_t memunit_distance(const memory_based_step_iterator<Iterator>& p1, | |
const memory_based_step_iterator<Iterator>& p2) { | |
return memunit_distance(p1.base(),p2.base()); | |
} | |
template <typename Iterator> | |
inline void memunit_advance(memory_based_step_iterator<Iterator>& p, | |
std::ptrdiff_t diff) { | |
memunit_advance(p.base(), diff); | |
} | |
template <typename Iterator> | |
inline memory_based_step_iterator<Iterator> | |
memunit_advanced(const memory_based_step_iterator<Iterator>& p, | |
std::ptrdiff_t diff) { | |
return memory_based_step_iterator<Iterator>(memunit_advanced(p.base(), diff),p.step()); | |
} | |
template <typename Iterator> | |
inline typename std::iterator_traits<Iterator>::reference | |
memunit_advanced_ref(const memory_based_step_iterator<Iterator>& p, | |
std::ptrdiff_t diff) { | |
return memunit_advanced_ref(p.base(), diff); | |
} | |
///////////////////////////// | |
// HasDynamicXStepTypeConcept | |
///////////////////////////// | |
template <typename Iterator> | |
struct dynamic_x_step_type<memory_based_step_iterator<Iterator> > { | |
typedef memory_based_step_iterator<Iterator> type; | |
}; | |
// For step iterators, pass the function object to the base | |
template <typename Iterator, typename Deref> | |
struct iterator_add_deref<memory_based_step_iterator<Iterator>,Deref> { | |
GIL_CLASS_REQUIRE(Deref, boost::gil, PixelDereferenceAdaptorConcept) | |
typedef memory_based_step_iterator<typename iterator_add_deref<Iterator, Deref>::type> type; | |
static type make(const memory_based_step_iterator<Iterator>& it, const Deref& d) { return type(iterator_add_deref<Iterator, Deref>::make(it.base(),d),it.step()); } | |
}; | |
//////////////////////////////////////////////////////////////////////////////////////// | |
/// make_step_iterator | |
//////////////////////////////////////////////////////////////////////////////////////// | |
template <typename I> typename dynamic_x_step_type<I>::type make_step_iterator(const I& it, std::ptrdiff_t step); | |
namespace detail { | |
// if the iterator is a plain base iterator (non-adaptor), wraps it in memory_based_step_iterator | |
template <typename I> | |
typename dynamic_x_step_type<I>::type make_step_iterator_impl(const I& it, std::ptrdiff_t step, mpl::false_) { | |
return memory_based_step_iterator<I>(it, step); | |
} | |
// If the iterator is compound, put the step in its base | |
template <typename I> | |
typename dynamic_x_step_type<I>::type make_step_iterator_impl(const I& it, std::ptrdiff_t step, mpl::true_) { | |
return make_step_iterator(it.base(), step); | |
} | |
// If the iterator is memory_based_step_iterator, change the step | |
template <typename BaseIt> | |
memory_based_step_iterator<BaseIt> make_step_iterator_impl(const memory_based_step_iterator<BaseIt>& it, std::ptrdiff_t step, mpl::true_) { | |
return memory_based_step_iterator<BaseIt>(it.base(), step); | |
} | |
} | |
/// \brief Constructs a step iterator from a base iterator and a step. | |
/// | |
/// To construct a step iterator from a given iterator Iterator and a given step, if Iterator does not | |
/// already have a dynamic step, we wrap it in a memory_based_step_iterator. Otherwise we | |
/// do a compile-time traversal of the chain of iterator adaptors to locate the step iterator | |
/// and then set it step to the new one. | |
/// | |
/// The step iterator of Iterator is not always memory_based_step_iterator<Iterator>. For example, Iterator may | |
/// already be a memory_based_step_iterator, in which case it will be inefficient to stack them; | |
/// we can obtain the same result by multiplying their steps. Note that for Iterator to be a | |
/// step iterator it does not necessarily have to have the form memory_based_step_iterator<J>. | |
/// The step iterator can be wrapped inside another iterator. Also, it may not have the | |
/// type memory_based_step_iterator, but it could be a user-provided type. | |
template <typename I> // Models MemoryBasedIteratorConcept, HasDynamicXStepTypeConcept | |
typename dynamic_x_step_type<I>::type make_step_iterator(const I& it, std::ptrdiff_t step) { | |
return detail::make_step_iterator_impl(it, step, typename is_iterator_adaptor<I>::type()); | |
} | |
} } // namespace boost::gil | |
#endif |