virtual_locator.hpp

//
// Copyright 2005-2007 Adobe Systems Incorporated
//
// Distributed under 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
//
#ifndef BOOST_GIL_VIRTUAL_LOCATOR_HPP
#define BOOST_GIL_VIRTUAL_LOCATOR_HPP

#include <boost/gil/dynamic_step.hpp>
#include <boost/gil/position_iterator.hpp>

#include <boost/assert.hpp>
#include <boost/iterator/iterator_facade.hpp>

namespace boost { namespace gil {

template <typename Deref, bool IsTransposed>        // A function object that given a point returns a reference. Models PixelDereferenceAdaptorConcept
class virtual_2d_locator : public pixel_2d_locator_base<virtual_2d_locator<Deref,IsTransposed>, position_iterator<Deref,IsTransposed>, position_iterator<Deref,1-IsTransposed>>
{
    using this_t = virtual_2d_locator<Deref,IsTransposed>;
public:
    using parent_t = pixel_2d_locator_base<virtual_2d_locator<Deref,IsTransposed>, position_iterator<Deref,IsTransposed>, position_iterator<Deref,1-IsTransposed>>;
    using const_t = virtual_2d_locator<typename Deref::const_t,IsTransposed>;

    using deref_fn_t = Deref;
    using point_t = typename parent_t::point_t;

    using coord_t = typename parent_t::coord_t;
    using x_coord_t = typename parent_t::x_coord_t;
    using y_coord_t = typename parent_t::y_coord_t;
    using x_iterator = typename parent_t::x_iterator;
    using y_iterator = typename parent_t::y_iterator;

    template <typename NewDeref> struct add_deref
    {
        using type = virtual_2d_locator<deref_compose<NewDeref,Deref>,IsTransposed>;
        static type make(const virtual_2d_locator<Deref,IsTransposed>& loc, const NewDeref& nderef) {
            return type(loc.pos(), loc.step(), deref_compose<NewDeref,Deref>(nderef,loc.deref_fn()));
        }
    };

    virtual_2d_locator(const point_t& p=point_t(0,0), const point_t& step=point_t(1,1), const deref_fn_t& d=deref_fn_t()) : _p(p,step,d) {}
    template <typename D, bool TR> virtual_2d_locator(const virtual_2d_locator<D,TR>& loc, coord_t y_step)
        : _p(loc.pos(), point_t(loc.step().x,loc.step().y*y_step),     loc.deref_fn()) {}

    template <typename D, bool TR>
    virtual_2d_locator(virtual_2d_locator<D, TR> const& loc, coord_t x_step, coord_t y_step, bool transpose = false)
        : _p(loc.pos()
        , transpose ?
            point_t(loc.step().x * y_step, loc.step().y * x_step) :
            point_t(loc.step().x * x_step, loc.step().y * y_step)
        , loc.deref_fn())
    {
        BOOST_ASSERT(transpose == (IsTransposed != TR));
    }

    template <typename D, bool TR> virtual_2d_locator(const virtual_2d_locator<D,TR>& pl) : _p(pl._p) {}
    virtual_2d_locator(const virtual_2d_locator& pl) : _p(pl._p) {}

    bool              operator==(const this_t& p) const { return _p==p._p; }

    x_iterator&       x()                               { return *gil_reinterpret_cast<x_iterator*>(this); }
    y_iterator&       y()                               { return _p; }
    x_iterator const& x()                         const { return *gil_reinterpret_cast_c<x_iterator const*>(this); }
    y_iterator const& y()                         const { return _p; }

    // Returns the y distance between two x_iterators given the difference of their x positions
    y_coord_t y_distance_to(const this_t& it2, x_coord_t) const { return (it2.pos()[1-IsTransposed] - pos()[1-IsTransposed])/step()[1-IsTransposed]; }
    bool      is_1d_traversable(x_coord_t)        const { return false; }   // is there no gap at the end of each row? I.e. can we use x_iterator to visit every pixel instead of nested loops?

    // Methods specific for virtual 2D locator
    const point_t&   pos()                        const { return _p.pos(); }
    const point_t&   step()                       const { return _p.step(); }
    const deref_fn_t& deref_fn()                  const { return _p.deref_fn(); }
private:
    template <typename D, bool TR> friend class virtual_2d_locator;
    y_iterator        _p;    // contains the current position, the step and the dereference object
};

//  PixelBasedConcept

template <typename D, bool TR>
struct channel_type<virtual_2d_locator<D,TR> > : public channel_type<typename virtual_2d_locator<D,TR>::parent_t> {
};

template <typename D, bool TR>
struct color_space_type<virtual_2d_locator<D,TR> > : public color_space_type<typename virtual_2d_locator<D,TR>::parent_t> {
};

template <typename D, bool TR>
struct channel_mapping_type<virtual_2d_locator<D,TR> > : public channel_mapping_type<typename virtual_2d_locator<D,TR>::parent_t> {
};

template <typename D, bool TR>
struct is_planar<virtual_2d_locator<D,TR> > : public is_planar<typename virtual_2d_locator<D,TR>::parent_t> {
};

//  HasDynamicXStepTypeConcept

template <typename D, bool TR>
struct dynamic_x_step_type<virtual_2d_locator<D,TR>>
{
    using type = virtual_2d_locator<D,TR>;
};

//  HasDynamicYStepTypeConcept

template <typename D, bool TR>
struct dynamic_y_step_type<virtual_2d_locator<D,TR>>
{
    using type = virtual_2d_locator<D,TR>;
};

//  HasTransposedTypeConcept

template <typename D, bool IsTransposed>
struct transposed_type<virtual_2d_locator<D,IsTransposed>>
{
    using type = virtual_2d_locator<D,1-IsTransposed>;
};

}}  // namespace boost::gil

#endif