boost/gil/image_view.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_IMAGE_VIEW_HPP #define BOOST_GIL_IMAGE_VIEW_HPP #include <boost/gil/dynamic_step.hpp> #include <boost/gil/iterator_from_2d.hpp> #include <cstddef> #include <iterator> namespace boost { namespace gil { //////////////////////////////////////////////////////////////////////////////////////// /// \class image_view /// \ingroup ImageViewModel PixelBasedModel /// \brief A lightweight object that interprets memory as a 2D array of pixels. Models ImageViewConcept,PixelBasedConcept,HasDynamicXStepTypeConcept,HasDynamicYStepTypeConcept,HasTransposedTypeConcept /// /// Image view consists of a pixel 2D locator (defining the mechanism for navigating in 2D) /// and the image dimensions. /// /// Image views to images are what ranges are to STL containers. They are lightweight objects, /// that don't own the pixels. It is the user's responsibility that the underlying data remains /// valid for the lifetime of the image view. /// /// Similar to iterators and ranges, constness of views does not extend to constness of pixels. /// A const \p image_view does not allow changing its location in memory (resizing, moving) but does /// not prevent one from changing the pixels. The latter requires an image view whose value_type /// is const. /// /// Images have interfaces consistent with STL 1D random access containers, so they can be used /// directly in STL algorithms like: /// \code /// std::fill(img.begin(), img.end(), red_pixel); /// \endcode /// /// In addition, horizontal, vertical and 2D random access iterators are provided. /// /// Note also that \p image_view does not require that its element type be a pixel. It could be /// instantiated with a locator whose \p value_type models only \p Regular. In this case the image /// view models the weaker RandomAccess2DImageViewConcept, and does not model PixelBasedConcept. /// Many generic algorithms don't require the elements to be pixels. /// //////////////////////////////////////////////////////////////////////////////////////// template <typename Loc> // Models 2D Pixel Locator class image_view { public: // aliases required by ConstRandomAccessNDImageViewConcept static const std::size_t num_dimensions=2; using value_type = typename Loc::value_type; using reference = typename Loc::reference; // result of dereferencing using coord_t = typename Loc::coord_t; // 1D difference type (same for all dimensions) using difference_type = coord_t; // result of operator-(1d_iterator,1d_iterator) using point_t = typename Loc::point_t; using locator = Loc; using const_t = image_view<typename Loc::const_t>; // same as this type, but over const values template <std::size_t D> struct axis { using coord_t = typename Loc::template axis<D>::coord_t; // difference_type along each dimension using iterator = typename Loc::template axis<D>::iterator; // 1D iterator type along each dimension }; using iterator = iterator_from_2d<Loc>; // 1D iterator type for each pixel left-to-right inside top-to-bottom using const_iterator = typename const_t::iterator; // may be used to examine, but not to modify values using const_reference = typename const_t::reference; // behaves as a const reference using pointer = typename std::iterator_traits<iterator>::pointer; // behaves as a pointer to the value type using reverse_iterator = std::reverse_iterator<iterator>; using size_type = std::size_t; // aliases required by ConstRandomAccess2DImageViewConcept using xy_locator = locator; using x_iterator = typename xy_locator::x_iterator; // pixel iterator along a row using y_iterator = typename xy_locator::y_iterator; // pixel iterator along a column using x_coord_t = typename xy_locator::x_coord_t; using y_coord_t = typename xy_locator::y_coord_t; template <typename Deref> struct add_deref { using type = image_view<typename Loc::template add_deref<Deref>::type>; static type make(const image_view<Loc>& iv, const Deref& d) { return type(iv.dimensions(), Loc::template add_deref<Deref>::make(iv.pixels(),d)); } }; image_view() : _dimensions(0,0) {} template <typename View> image_view(const View& iv) : _dimensions(iv.dimensions()), _pixels(iv.pixels()) {} template <typename L2> image_view(const point_t& sz , const L2& loc) : _dimensions(sz), _pixels(loc) {} template <typename L2> image_view(coord_t width, coord_t height, const L2& loc) : _dimensions(x_coord_t(width),y_coord_t(height)), _pixels(loc) {} template <typename View> image_view& operator=(const View& iv) { _pixels=iv.pixels(); _dimensions=iv.dimensions(); return *this; } image_view& operator=(const image_view& iv) { _pixels=iv.pixels(); _dimensions=iv.dimensions(); return *this; } template <typename View> bool operator==(const View& v) const { return pixels()==v.pixels() && dimensions()==v.dimensions(); } template <typename View> bool operator!=(const View& v) const { return !(*this==v); } template <typename L2> friend void swap(image_view<L2>& x, image_view<L2>& y); /// \brief Exchanges the elements of the current view with those of \a other /// in constant time. /// /// \note Required by the Collection concept /// \see https://www.boost.org/libs/utility/Collection.html void swap(image_view<Loc>& other) { using boost::gil::swap; swap(*this, other); } /// \brief Returns true if the view has no elements, false otherwise. /// /// \note Required by the Collection concept /// \see https://www.boost.org/libs/utility/Collection.html bool empty() const { return !(width() > 0 && height() > 0); } /// \brief Returns a reference to the first element in raster order. /// /// \note Required by the ForwardCollection, since view model the concept. /// \see https://www.boost.org/libs/utility/Collection.html reference front() const { return *begin(); } /// \brief Returns a reference to the last element in raster order. /// /// \note Required by the ForwardCollection, since view model the concept. /// \see https://www.boost.org/libs/utility/Collection.html reference back() const { return *rbegin(); } const point_t& dimensions() const { return _dimensions; } const locator& pixels() const { return _pixels; } x_coord_t width() const { return dimensions().x; } y_coord_t height() const { return dimensions().y; } std::size_t num_channels() const { return gil::num_channels<value_type>::value; } bool is_1d_traversable() const { return _pixels.is_1d_traversable(width()); } //\{@ /// \name 1D navigation size_type size() const { return width()*height(); } iterator begin() const { return iterator(_pixels,_dimensions.x); } iterator end() const { return begin()+(difference_type)size(); } // potential performance problem! reverse_iterator rbegin() const { return reverse_iterator(end()); } reverse_iterator rend() const { return reverse_iterator(begin()); } reference operator[](difference_type i) const { return begin()[i]; } // potential performance problem! iterator at(difference_type i)const { return begin()+i; } iterator at(const point_t& p) const { return begin()+p.y*width()+p.x; } iterator at(x_coord_t x, y_coord_t y)const { return begin()+y*width()+x; } //\}@ //\{@ /// \name 2-D navigation reference operator()(const point_t& p) const { return _pixels(p.x,p.y); } reference operator()(x_coord_t x, y_coord_t y)const { return _pixels(x,y); } template <std::size_t D> typename axis<D>::iterator axis_iterator(const point_t& p) const { return _pixels.template axis_iterator<D>(p); } xy_locator xy_at(x_coord_t x, y_coord_t y) const { return _pixels+point_t(x_coord_t(x),y_coord_t(y)); } locator xy_at(const point_t& p) const { return _pixels+p; } //\}@ //\{@ /// \name X navigation x_iterator x_at(x_coord_t x, y_coord_t y) const { return _pixels.x_at(x,y); } x_iterator x_at(const point_t& p) const { return _pixels.x_at(p); } x_iterator row_begin(y_coord_t y) const { return x_at(0,y); } x_iterator row_end(y_coord_t y) const { return x_at(width(),y); } //\}@ //\{@ /// \name Y navigation y_iterator y_at(x_coord_t x, y_coord_t y) const { return xy_at(x,y).y(); } y_iterator y_at(const point_t& p) const { return xy_at(p).y(); } y_iterator col_begin(x_coord_t x) const { return y_at(x,0); } y_iterator col_end(x_coord_t x) const { return y_at(x,height()); } //\}@ private: template <typename L2> friend class image_view; point_t _dimensions; xy_locator _pixels; }; template <typename L2> inline void swap(image_view<L2>& x, image_view<L2>& y) { using std::swap; swap(x._dimensions,y._dimensions); swap(x._pixels, y._pixels); // TODO: Extend further } ///////////////////////////// // PixelBasedConcept ///////////////////////////// template <typename L> struct channel_type<image_view<L> > : public channel_type<L> {}; template <typename L> struct color_space_type<image_view<L> > : public color_space_type<L> {}; template <typename L> struct channel_mapping_type<image_view<L> > : public channel_mapping_type<L> {}; template <typename L> struct is_planar<image_view<L> > : public is_planar<L> {}; ///////////////////////////// // HasDynamicXStepTypeConcept ///////////////////////////// template <typename L> struct dynamic_x_step_type<image_view<L> > { using type = image_view<typename dynamic_x_step_type<L>::type>; }; ///////////////////////////// // HasDynamicYStepTypeConcept ///////////////////////////// template <typename L> struct dynamic_y_step_type<image_view<L> > { using type = image_view<typename dynamic_y_step_type<L>::type>; }; ///////////////////////////// // HasTransposedTypeConcept ///////////////////////////// template <typename L> struct transposed_type<image_view<L> > { using type = image_view<typename transposed_type<L>::type>; }; }} // namespace boost::gil #endif