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