Chris@16: /*
Chris@16:     Copyright 2005-2007 Adobe Systems Incorporated
Chris@16:    
Chris@16:     Use, modification and distribution are subject to the Boost Software License,
Chris@16:     Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
Chris@16:     http://www.boost.org/LICENSE_1_0.txt).
Chris@16: 
Chris@16:     See http://opensource.adobe.com/gil for most recent version including documentation.
Chris@16: */
Chris@16: 
Chris@16: /*************************************************************************************************/
Chris@16: 
Chris@16: #ifndef GIL_IMAGE_VIEW_FACTORY_HPP
Chris@16: #define GIL_IMAGE_VIEW_FACTORY_HPP
Chris@16: 
Chris@16: /*!
Chris@16: /// \file               
Chris@16: /// \brief Methods for constructing image views from raw data or other image views
Chris@16: /// \author Lubomir Bourdev and Hailin Jin \n
Chris@16: ///         Adobe Systems Incorporated
Chris@16: /// \date   2005-2007 \n Last updated on March 9, 2007
Chris@16: /// Methods for creating shallow image views from raw pixel data or from other image views - 
Chris@16: /// flipping horizontally or vertically, axis-aligned rotation, a subimage, subsampled 
Chris@16: /// or n-th channel image view. Derived image views are shallow copies and are fast to construct.
Chris@16: */
Chris@16: 
Chris@16: #include <cassert>
Chris@16: #include <cstddef>
Chris@16: #include "gil_config.hpp"
Chris@16: #include "metafunctions.hpp"
Chris@16: #include "gray.hpp"
Chris@16: #include "color_convert.hpp"
Chris@16: 
Chris@16: /// \defgroup ImageViewConstructors Image View From Raw Data
Chris@16: /// \ingroup ImageViewAlgorithm
Chris@16: /// \brief Methods for constructing image views from raw data and for getting raw data from views
Chris@16: 
Chris@16: /// \defgroup ImageViewTransformations Image View Transformations
Chris@16: /// \ingroup ImageViewAlgorithm
Chris@16: /// \brief Methods for constructing one image view from another
Chris@16: 
Chris@16: namespace boost { namespace gil {
Chris@16: struct default_color_converter;
Chris@16: 
Chris@16: template <typename T> struct dynamic_x_step_type;
Chris@16: template <typename T> struct dynamic_y_step_type;
Chris@16: template <typename T> struct transposed_type;
Chris@16: 
Chris@16: /// \brief Returns the type of a view that has a dynamic step along both X and Y
Chris@16: /// \ingroup ImageViewTransformations
Chris@16: template <typename View> 
Chris@16: struct dynamic_xy_step_type : public dynamic_y_step_type<typename dynamic_x_step_type<View>::type> {};
Chris@16: 
Chris@16: /// \brief Returns the type of a transposed view that has a dynamic step along both X and Y
Chris@16: /// \ingroup ImageViewTransformations
Chris@16: template <typename View> 
Chris@16: struct dynamic_xy_step_transposed_type : public dynamic_xy_step_type<typename transposed_type<View>::type> {};
Chris@16: 
Chris@16: 
Chris@16: /// \ingroup ImageViewConstructors
Chris@16: /// \brief Constructing image views from raw interleaved pixel data
Chris@16: template <typename Iterator>
Chris@16: typename type_from_x_iterator<Iterator>::view_t
Chris@16: interleaved_view(std::size_t width, std::size_t height,
Chris@16:                  Iterator pixels, std::ptrdiff_t rowsize_in_bytes) {
Chris@16:     typedef typename type_from_x_iterator<Iterator>::view_t RView;
Chris@16:     return RView(width, height, typename RView::locator(pixels, rowsize_in_bytes));
Chris@16: }
Chris@16: 
Chris@16: /// \ingroup ImageViewConstructors
Chris@16: /// \brief Constructing image views from raw interleaved pixel data
Chris@16: template <typename Iterator>
Chris@16: typename type_from_x_iterator<Iterator>::view_t
Chris@16: interleaved_view(point2<std::size_t> dim,
Chris@16:                  Iterator pixels, std::ptrdiff_t rowsize_in_bytes) {
Chris@16:     typedef typename type_from_x_iterator<Iterator>::view_t RView;
Chris@16:     return RView(dim, typename RView::locator(pixels, rowsize_in_bytes));
Chris@16: }
Chris@16: 
Chris@16: /////////////////////////////
Chris@16: //  interleaved_view_get_raw_data, planar_view_get_raw_data - return pointers to the raw data (the channels) of a basic homogeneous view.
Chris@16: /////////////////////////////
Chris@16: 
Chris@16: namespace detail {
Chris@16:     template <typename View, bool IsMutable> struct channel_pointer_type_impl;
Chris@16: 
Chris@16:     template <typename View> struct channel_pointer_type_impl<View, true> {
Chris@16:         typedef       typename channel_type<View>::type* type;
Chris@16:     };
Chris@16:     template <typename View> struct channel_pointer_type_impl<View, false> {
Chris@16:         typedef const typename channel_type<View>::type* type;
Chris@16:     };
Chris@16: 
Chris@16:     template <typename View> struct channel_pointer_type
Chris@16:         : public channel_pointer_type_impl<View, view_is_mutable<View>::value> {};
Chris@16: } // namespace detail
Chris@16: 
Chris@16: /// \ingroup ImageViewConstructors
Chris@16: /// \brief Returns C pointer to the the channels of an interleaved homogeneous view.
Chris@16: template <typename HomogeneousView>
Chris@16: typename detail::channel_pointer_type<HomogeneousView>::type interleaved_view_get_raw_data(const HomogeneousView& view) {
Chris@16:     BOOST_STATIC_ASSERT((!is_planar<HomogeneousView>::value && view_is_basic<HomogeneousView>::value));
Chris@16:     BOOST_STATIC_ASSERT((boost::is_pointer<typename HomogeneousView::x_iterator>::value));
Chris@16: 
Chris@16:     return &gil::at_c<0>(view(0,0));
Chris@16: }
Chris@16: 
Chris@16: /// \ingroup ImageViewConstructors
Chris@16: /// \brief Returns C pointer to the the channels of a given color plane of a planar homogeneous view.
Chris@16: template <typename HomogeneousView>
Chris@16: typename detail::channel_pointer_type<HomogeneousView>::type planar_view_get_raw_data(const HomogeneousView& view, int plane_index) {
Chris@16:     BOOST_STATIC_ASSERT((is_planar<HomogeneousView>::value && view_is_basic<HomogeneousView>::value));
Chris@16:     return dynamic_at_c(view.row_begin(0),plane_index);
Chris@16: }
Chris@16: 
Chris@16: 
Chris@16: /// \defgroup ImageViewTransformationsColorConvert color_converted_view
Chris@16: /// \ingroup ImageViewTransformations
Chris@16: /// \brief Color converted view of another view
Chris@16: 
Chris@16: /// \ingroup ImageViewTransformationsColorConvert PixelDereferenceAdaptorModel
Chris@16: /// \brief Function object that given a source pixel, returns it converted to a given color space and channel depth. Models: PixelDereferenceAdaptorConcept
Chris@16: ///
Chris@16: /// Useful in constructing a color converted view over a given image view
Chris@16: template <typename SrcConstRefP, typename DstP, typename CC=default_color_converter >        // const_reference to the source pixel and destination pixel value
Chris@16: class color_convert_deref_fn : public deref_base<color_convert_deref_fn<SrcConstRefP,DstP,CC>, DstP, DstP, const DstP&, SrcConstRefP, DstP, false> {
Chris@16: private:
Chris@16:     CC _cc;                     // color-converter
Chris@16: public:
Chris@16:     color_convert_deref_fn() {}
Chris@16:     color_convert_deref_fn(CC cc_in) : _cc(cc_in) {}
Chris@16: 
Chris@16:     DstP operator()(SrcConstRefP srcP) const {
Chris@16:         DstP dstP;
Chris@16:         _cc(srcP,dstP);
Chris@16:         return dstP;
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: namespace detail {
Chris@16:     // Add color converter upon dereferencing
Chris@16:     template <typename SrcView, typename CC, typename DstP, typename SrcP>
Chris@16:     struct _color_converted_view_type {
Chris@16:     private:
Chris@16:         typedef color_convert_deref_fn<typename SrcView::const_t::reference,DstP,CC> deref_t;
Chris@16:         typedef typename SrcView::template add_deref<deref_t> add_ref_t;
Chris@16:     public:
Chris@16:         typedef typename add_ref_t::type type;
Chris@16:         static type make(const SrcView& sv,CC cc) {return add_ref_t::make(sv,deref_t(cc));}
Chris@16:     };
Chris@16: 
Chris@16:     // If the Src view has the same pixel type as the target, there is no need for color conversion
Chris@16:     template <typename SrcView, typename CC, typename DstP>
Chris@16:     struct _color_converted_view_type<SrcView,CC,DstP,DstP> {
Chris@16:         typedef SrcView type;
Chris@16:         static type make(const SrcView& sv,CC) {return sv;}
Chris@16:     };
Chris@16: } // namespace detail
Chris@16: 
Chris@16: 
Chris@16: /// \brief Returns the type of a view that does color conversion upon dereferencing its pixels 
Chris@16: /// \ingroup ImageViewTransformationsColorConvert
Chris@16: template <typename SrcView, typename DstP, typename CC=default_color_converter>
Chris@16: struct color_converted_view_type : public detail::_color_converted_view_type<SrcView,
Chris@16:                                                                              CC,
Chris@16:                                                                              DstP,
Chris@16:                                                                              typename SrcView::value_type> {
Chris@16:     GIL_CLASS_REQUIRE(DstP, boost::gil, MutablePixelConcept)//why does it have to be mutable???
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: /// \ingroup ImageViewTransformationsColorConvert
Chris@16: /// \brief view of a different color space with a user defined color-converter
Chris@16: template <typename DstP, typename View, typename CC>
Chris@16: inline typename color_converted_view_type<View,DstP,CC>::type color_converted_view(const View& src,CC cc) {
Chris@16:     return color_converted_view_type<View,DstP,CC>::make(src,cc);
Chris@16: }
Chris@16: 
Chris@16: /// \ingroup ImageViewTransformationsColorConvert
Chris@16: /// \brief overload of generic color_converted_view with the default color-converter
Chris@16: template <typename DstP, typename View>
Chris@16: inline typename color_converted_view_type<View,DstP>::type
Chris@16: color_converted_view(const View& src) {
Chris@16:     return color_converted_view<DstP>(src,default_color_converter());
Chris@16: }
Chris@16: 
Chris@16: /// \defgroup ImageViewTransformationsFlipUD flipped_up_down_view
Chris@16: /// \ingroup ImageViewTransformations
Chris@16: /// \brief view of a view flipped up-to-down
Chris@16: 
Chris@16: /// \ingroup ImageViewTransformationsFlipUD
Chris@16: template <typename View>
Chris@16: inline typename dynamic_y_step_type<View>::type flipped_up_down_view(const View& src) { 
Chris@16:     typedef typename dynamic_y_step_type<View>::type RView;
Chris@16:     return RView(src.dimensions(),typename RView::xy_locator(src.xy_at(0,src.height()-1),-1));
Chris@16: }
Chris@16: 
Chris@16: /// \defgroup ImageViewTransformationsFlipLR flipped_left_right_view
Chris@16: /// \ingroup ImageViewTransformations
Chris@16: /// \brief view of a view flipped left-to-right
Chris@16: 
Chris@16: /// \ingroup ImageViewTransformationsFlipLR
Chris@16: template <typename View> 
Chris@16: inline typename dynamic_x_step_type<View>::type flipped_left_right_view(const View& src) {
Chris@16:     typedef typename dynamic_x_step_type<View>::type RView;
Chris@16:     return RView(src.dimensions(),typename RView::xy_locator(src.xy_at(src.width()-1,0),-1,1));
Chris@16: }
Chris@16: 
Chris@16: /// \defgroup ImageViewTransformationsTransposed transposed_view
Chris@16: /// \ingroup ImageViewTransformations
Chris@16: /// \brief view of a view transposed
Chris@16: 
Chris@16: /// \ingroup ImageViewTransformationsTransposed
Chris@16: template <typename View>
Chris@16: inline typename dynamic_xy_step_transposed_type<View>::type transposed_view(const View& src) {
Chris@16:     typedef typename dynamic_xy_step_transposed_type<View>::type RView;
Chris@16:     return RView(src.height(),src.width(),typename RView::xy_locator(src.xy_at(0,0),1,1,true));
Chris@16: }
Chris@16: 
Chris@16: /// \defgroup ImageViewTransformations90CW rotated90cw_view
Chris@16: /// \ingroup ImageViewTransformations
Chris@16: /// \brief view of a view rotated 90 degrees clockwise
Chris@16: 
Chris@16: /// \ingroup ImageViewTransformations90CW
Chris@16: template <typename View> 
Chris@16: inline typename dynamic_xy_step_transposed_type<View>::type rotated90cw_view(const View& src) {
Chris@16:     typedef typename dynamic_xy_step_transposed_type<View>::type RView;
Chris@16:     return RView(src.height(),src.width(),typename RView::xy_locator(src.xy_at(0,src.height()-1),-1,1,true));
Chris@16: }
Chris@16: 
Chris@16: /// \defgroup ImageViewTransformations90CCW rotated90ccw_view
Chris@16: /// \ingroup ImageViewTransformations
Chris@16: /// \brief view of a view rotated 90 degrees counter-clockwise
Chris@16: 
Chris@16: /// \ingroup ImageViewTransformations90CCW
Chris@16: template <typename View> 
Chris@16: inline typename dynamic_xy_step_transposed_type<View>::type rotated90ccw_view(const View& src) {
Chris@16:     typedef typename dynamic_xy_step_transposed_type<View>::type RView;
Chris@16:     return RView(src.height(),src.width(),typename RView::xy_locator(src.xy_at(src.width()-1,0),1,-1,true));
Chris@16: }
Chris@16: 
Chris@16: /// \defgroup ImageViewTransformations180 rotated180_view
Chris@16: /// \ingroup ImageViewTransformations
Chris@16: /// \brief view of a view rotated 180 degrees
Chris@16: 
Chris@16: /// \ingroup ImageViewTransformations180
Chris@16: template <typename View> 
Chris@16: inline typename dynamic_xy_step_type<View>::type rotated180_view(const View& src) {
Chris@16:     typedef typename dynamic_xy_step_type<View>::type RView;
Chris@16:     return RView(src.dimensions(),typename RView::xy_locator(src.xy_at(src.width()-1,src.height()-1),-1,-1));
Chris@16: }
Chris@16: 
Chris@16: /// \defgroup ImageViewTransformationsSubimage subimage_view
Chris@16: /// \ingroup ImageViewTransformations
Chris@16: /// \brief view of an axis-aligned rectangular area within an image_view
Chris@16: 
Chris@16: /// \ingroup ImageViewTransformationsSubimage
Chris@16: template <typename View> 
Chris@16: inline View subimage_view(const View& src, const typename View::point_t& topleft, const typename View::point_t& dimensions) {
Chris@16:     return View(dimensions,src.xy_at(topleft));
Chris@16: }
Chris@16: 
Chris@16: /// \ingroup ImageViewTransformationsSubimage
Chris@16: template <typename View> 
Chris@16: inline View subimage_view(const View& src, int xMin, int yMin, int width, int height) {
Chris@16:     return View(width,height,src.xy_at(xMin,yMin));
Chris@16: }
Chris@16: 
Chris@16: /// \defgroup ImageViewTransformationsSubsampled subsampled_view
Chris@16: /// \ingroup ImageViewTransformations
Chris@16: /// \brief view of a subsampled version of an image_view, stepping over a number of channels in X and number of rows in Y
Chris@16: 
Chris@16: /// \ingroup ImageViewTransformationsSubsampled
Chris@16: template <typename View> 
Chris@16: inline typename dynamic_xy_step_type<View>::type subsampled_view(const View& src, typename View::coord_t xStep, typename View::coord_t yStep) {
Chris@16:     assert(xStep>0 && yStep>0);
Chris@16:     typedef typename dynamic_xy_step_type<View>::type RView;
Chris@16:     return RView((src.width()+(xStep-1))/xStep,(src.height()+(yStep-1))/yStep,
Chris@16:                                           typename RView::xy_locator(src.xy_at(0,0),xStep,yStep));
Chris@16: }
Chris@16: 
Chris@16: /// \ingroup ImageViewTransformationsSubsampled
Chris@16: template <typename View> 
Chris@16: inline typename dynamic_xy_step_type<View>::type subsampled_view(const View& src, const typename View::point_t& step) { 
Chris@16:     return subsampled_view(src,step.x,step.y);
Chris@16: }
Chris@16: 
Chris@16: /// \defgroup ImageViewTransformationsNthChannel nth_channel_view
Chris@16: /// \ingroup ImageViewTransformations
Chris@16: /// \brief single-channel (grayscale) view of the N-th channel of a given image_view
Chris@16: 
Chris@16: namespace detail {
Chris@16:     template <typename View, bool AreChannelsTogether> struct __nth_channel_view_basic;
Chris@16: 
Chris@16:     // nth_channel_view when the channels are not adjacent in memory. This can happen for multi-channel interleaved images 
Chris@16:     // or images with a step
Chris@16:     template <typename View>
Chris@16:     struct __nth_channel_view_basic<View,false> {
Chris@16:         typedef typename view_type<typename channel_type<View>::type, gray_layout_t, false, true, view_is_mutable<View>::value>::type type;
Chris@16: 
Chris@16:         static type make(const View& src, int n) {
Chris@16:             typedef typename type::xy_locator                             locator_t;
Chris@16:             typedef typename type::x_iterator                            x_iterator_t;
Chris@16:             typedef typename iterator_adaptor_get_base<x_iterator_t>::type x_iterator_base_t;
Chris@16:             x_iterator_t sit(x_iterator_base_t(&(src(0,0)[n])),src.pixels().pixel_size());
Chris@16:             return type(src.dimensions(),locator_t(sit, src.pixels().row_size()));
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     // nth_channel_view when the channels are together in memory (true for simple grayscale or planar images)
Chris@16:     template <typename View>
Chris@16:     struct __nth_channel_view_basic<View,true> {
Chris@16:         typedef typename view_type<typename channel_type<View>::type, gray_layout_t, false, false, view_is_mutable<View>::value>::type type;
Chris@16:         static type make(const View& src, int n) {
Chris@16:             typedef typename type::x_iterator x_iterator_t;
Chris@16:             return interleaved_view(src.width(),src.height(),(x_iterator_t)&(src(0,0)[n]), src.pixels().row_size());
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     template <typename View, bool IsBasic> struct __nth_channel_view;
Chris@16: 
Chris@16:     // For basic (memory-based) views dispatch to __nth_channel_view_basic
Chris@16:     template <typename View> struct __nth_channel_view<View,true> {
Chris@16:     private:
Chris@16:         typedef typename View::x_iterator src_x_iterator;
Chris@16: 
Chris@16:         // Determines whether the channels of a given pixel iterator are adjacent in memory.
Chris@16:         // Planar and grayscale iterators have channels adjacent in memory, whereas multi-channel interleaved and iterators with non-fundamental step do not.
Chris@16:         BOOST_STATIC_CONSTANT(bool, adjacent=
Chris@16:                               !iterator_is_step<src_x_iterator>::value &&
Chris@16:                               (is_planar<src_x_iterator>::value ||
Chris@16:                               num_channels<View>::value==1));
Chris@16:     public:
Chris@16:         typedef typename __nth_channel_view_basic<View,adjacent>::type type;
Chris@16: 
Chris@16:         static type make(const View& src, int n) {
Chris@16:             return __nth_channel_view_basic<View,adjacent>::make(src,n);
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     /// \brief Function object that returns a grayscale reference of the N-th channel of a given reference. Models: PixelDereferenceAdaptorConcept.
Chris@16:     /// \ingroup PixelDereferenceAdaptorModel
Chris@16:     ///
Chris@16:     /// If the input is a pixel value or constant reference, the function object is immutable. Otherwise it is mutable (and returns non-const reference to the n-th channel)
Chris@16:     template <typename SrcP>        // SrcP is a reference to PixelConcept (could be pixel value or const/non-const reference)
Chris@16:                                     // Examples: pixel<T,L>, pixel<T,L>&, const pixel<T,L>&, planar_pixel_reference<T&,L>, planar_pixel_reference<const T&,L>
Chris@16:     struct nth_channel_deref_fn {
Chris@16:         BOOST_STATIC_CONSTANT(bool, is_mutable=pixel_is_reference<SrcP>::value && pixel_reference_is_mutable<SrcP>::value);
Chris@16:     private:
Chris@16:         typedef typename remove_reference<SrcP>::type src_pixel_t;
Chris@16:         typedef typename channel_type<src_pixel_t>::type channel_t;
Chris@16:         typedef typename src_pixel_t::const_reference const_ref_t;
Chris@16:         typedef typename pixel_reference_type<channel_t,gray_layout_t,false,is_mutable>::type ref_t;
Chris@16:     public:
Chris@16:         typedef nth_channel_deref_fn<const_ref_t>                                        const_t;
Chris@16:         typedef typename pixel_value_type<channel_t,gray_layout_t>::type                 value_type;
Chris@16:         typedef typename pixel_reference_type<channel_t,gray_layout_t,false,false>::type const_reference;
Chris@16:         typedef SrcP                                                                     argument_type;
Chris@16:         typedef typename mpl::if_c<is_mutable, ref_t, value_type>::type                  reference;
Chris@16:         typedef reference                                                                result_type;
Chris@16: 
Chris@16:         nth_channel_deref_fn(int n=0) : _n(n) {}
Chris@16:         template <typename P> nth_channel_deref_fn(const nth_channel_deref_fn<P>& d) : _n(d._n) {}
Chris@16: 
Chris@16:         int _n;        // the channel to use
Chris@16: 
Chris@16:         result_type operator()(argument_type srcP) const { 
Chris@16:             return result_type(srcP[_n]); 
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     template <typename View> struct __nth_channel_view<View,false> {
Chris@16:     private:
Chris@16:         typedef nth_channel_deref_fn<typename View::reference> deref_t;
Chris@16:         typedef typename View::template add_deref<deref_t>   AD;
Chris@16:     public:
Chris@16:         typedef typename AD::type type;
Chris@16:         static type make(const View& src, int n) {
Chris@16:             return AD::make(src, deref_t(n));
Chris@16:         }
Chris@16:     };
Chris@16: } // namespace detail
Chris@16: 
Chris@16: /// \brief Given a source image view type View, returns the type of an image view over a single channel of View
Chris@16: /// \ingroup ImageViewTransformationsNthChannel
Chris@16: ///
Chris@16: /// If the channels in the source view are adjacent in memory (such as planar non-step view or single-channel view) then the
Chris@16: /// return view is a single-channel non-step view.
Chris@16: /// If the channels are non-adjacent (interleaved and/or step view) then the return view is a single-channel step view.
Chris@16: template <typename View>
Chris@16: struct nth_channel_view_type {
Chris@16: private:
Chris@16:     GIL_CLASS_REQUIRE(View, boost::gil, ImageViewConcept)
Chris@16:     typedef detail::__nth_channel_view<View,view_is_basic<View>::value> VB;
Chris@16: public:
Chris@16:     typedef typename VB::type type;
Chris@16:     static type make(const View& src, int n) { return VB::make(src,n); }
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: /// \ingroup ImageViewTransformationsNthChannel
Chris@16: template <typename View>
Chris@16: typename nth_channel_view_type<View>::type nth_channel_view(const View& src, int n) {
Chris@16:     return nth_channel_view_type<View>::make(src,n);
Chris@16: }
Chris@16: 
Chris@16: 
Chris@16: 
Chris@16: 
Chris@16: 
Chris@16: 
Chris@16: 
Chris@16: /// \defgroup ImageViewTransformationsKthChannel kth_channel_view
Chris@16: /// \ingroup ImageViewTransformations
Chris@16: /// \brief single-channel (grayscale) view of the K-th channel of a given image_view. The channel index is a template parameter
Chris@16: 
Chris@16: namespace detail {
Chris@16:     template <int K, typename View, bool AreChannelsTogether> struct __kth_channel_view_basic;
Chris@16: 
Chris@16:     // kth_channel_view when the channels are not adjacent in memory. This can happen for multi-channel interleaved images 
Chris@16:     // or images with a step
Chris@16:     template <int K, typename View>
Chris@16:     struct __kth_channel_view_basic<K,View,false> {
Chris@16:     private:
Chris@16:         typedef typename kth_element_type<typename View::value_type,K>::type channel_t;
Chris@16:     public:
Chris@16:         typedef typename view_type<channel_t, gray_layout_t, false, true, view_is_mutable<View>::value>::type type;
Chris@16: 
Chris@16:         static type make(const View& src) {
Chris@16:             typedef typename type::xy_locator                             locator_t;
Chris@16:             typedef typename type::x_iterator                            x_iterator_t;
Chris@16:             typedef typename iterator_adaptor_get_base<x_iterator_t>::type x_iterator_base_t;
Chris@16:             x_iterator_t sit(x_iterator_base_t(&gil::at_c<K>(src(0,0))),src.pixels().pixel_size());
Chris@16:             return type(src.dimensions(),locator_t(sit, src.pixels().row_size()));
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     // kth_channel_view when the channels are together in memory (true for simple grayscale or planar images)
Chris@16:     template <int K, typename View>
Chris@16:     struct __kth_channel_view_basic<K,View,true> {
Chris@16:     private:
Chris@16:         typedef typename kth_element_type<typename View::value_type, K>::type channel_t;
Chris@16:     public:
Chris@16:         typedef typename view_type<channel_t, gray_layout_t, false, false, view_is_mutable<View>::value>::type type;
Chris@16:         static type make(const View& src) {
Chris@16:             typedef typename type::x_iterator x_iterator_t;
Chris@16:             return interleaved_view(src.width(),src.height(),(x_iterator_t)&gil::at_c<K>(src(0,0)), src.pixels().row_size());
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     template <int K, typename View, bool IsBasic> struct __kth_channel_view;
Chris@16: 
Chris@16:     // For basic (memory-based) views dispatch to __kth_channel_view_basic
Chris@16:     template <int K, typename View> struct __kth_channel_view<K,View,true> {
Chris@16:     private:
Chris@16:         typedef typename View::x_iterator src_x_iterator;
Chris@16: 
Chris@16:         // Determines whether the channels of a given pixel iterator are adjacent in memory.
Chris@16:         // Planar and grayscale iterators have channels adjacent in memory, whereas multi-channel interleaved and iterators with non-fundamental step do not.
Chris@16:         BOOST_STATIC_CONSTANT(bool, adjacent=
Chris@16:                               !iterator_is_step<src_x_iterator>::value &&
Chris@16:                               (is_planar<src_x_iterator>::value ||
Chris@16:                               num_channels<View>::value==1));
Chris@16:     public:
Chris@16:         typedef typename __kth_channel_view_basic<K,View,adjacent>::type type;
Chris@16: 
Chris@16:         static type make(const View& src) {
Chris@16:             return __kth_channel_view_basic<K,View,adjacent>::make(src);
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     /// \brief Function object that returns a grayscale reference of the K-th channel (specified as a template parameter) of a given reference. Models: PixelDereferenceAdaptorConcept.
Chris@16:     /// \ingroup PixelDereferenceAdaptorModel
Chris@16:     ///
Chris@16:     /// If the input is a pixel value or constant reference, the function object is immutable. Otherwise it is mutable (and returns non-const reference to the k-th channel)
Chris@16:     template <int K, typename SrcP>        // SrcP is a reference to PixelConcept (could be pixel value or const/non-const reference)
Chris@16:                                     // Examples: pixel<T,L>, pixel<T,L>&, const pixel<T,L>&, planar_pixel_reference<T&,L>, planar_pixel_reference<const T&,L>
Chris@16:     struct kth_channel_deref_fn {
Chris@16:         BOOST_STATIC_CONSTANT(bool, is_mutable=pixel_is_reference<SrcP>::value && pixel_reference_is_mutable<SrcP>::value);
Chris@16:     private:
Chris@16:         typedef typename remove_reference<SrcP>::type src_pixel_t;
Chris@16:         typedef typename kth_element_type<src_pixel_t, K>::type channel_t;
Chris@16:         typedef typename src_pixel_t::const_reference const_ref_t;
Chris@16:         typedef typename pixel_reference_type<channel_t,gray_layout_t,false,is_mutable>::type ref_t;
Chris@16:     public:
Chris@16:         typedef kth_channel_deref_fn<K,const_ref_t>                               const_t;
Chris@16:         typedef typename pixel_value_type<channel_t,gray_layout_t>::type          value_type;
Chris@16:         typedef typename pixel_reference_type<channel_t,gray_layout_t,false,false>::type const_reference;
Chris@16:         typedef SrcP                                                              argument_type;
Chris@16:         typedef typename mpl::if_c<is_mutable, ref_t, value_type>::type           reference;
Chris@16:         typedef reference                                                         result_type;
Chris@16: 
Chris@16:         kth_channel_deref_fn() {}
Chris@16:         template <typename P> kth_channel_deref_fn(const kth_channel_deref_fn<K,P>&) {}
Chris@16: 
Chris@16:         result_type operator()(argument_type srcP) const { 
Chris@16:             return result_type(gil::at_c<K>(srcP));
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     template <int K, typename View> struct __kth_channel_view<K,View,false> {
Chris@16:     private:
Chris@16:         typedef kth_channel_deref_fn<K,typename View::reference> deref_t;
Chris@16:         typedef typename View::template add_deref<deref_t>   AD;
Chris@16:     public:
Chris@16:         typedef typename AD::type type;
Chris@16:         static type make(const View& src) {
Chris@16:             return AD::make(src, deref_t());
Chris@16:         }
Chris@16:     };
Chris@16: } // namespace detail
Chris@16: 
Chris@16: /// \brief Given a source image view type View, returns the type of an image view over a given channel of View.
Chris@16: /// \ingroup ImageViewTransformationsKthChannel
Chris@16: ///
Chris@16: /// If the channels in the source view are adjacent in memory (such as planar non-step view or single-channel view) then the
Chris@16: /// return view is a single-channel non-step view.
Chris@16: /// If the channels are non-adjacent (interleaved and/or step view) then the return view is a single-channel step view.
Chris@16: template <int K, typename View>
Chris@16: struct kth_channel_view_type {
Chris@16: private:
Chris@16:     GIL_CLASS_REQUIRE(View, boost::gil, ImageViewConcept)
Chris@16:     typedef detail::__kth_channel_view<K,View,view_is_basic<View>::value> VB;
Chris@16: public:
Chris@16:     typedef typename VB::type type;
Chris@16:     static type make(const View& src) { return VB::make(src); }
Chris@16: };
Chris@16: 
Chris@16: /// \ingroup ImageViewTransformationsKthChannel
Chris@16: template <int K, typename View>
Chris@16: typename kth_channel_view_type<K,View>::type kth_channel_view(const View& src) {
Chris@16:     return kth_channel_view_type<K,View>::make(src);
Chris@16: }
Chris@16: 
Chris@16: } }  // namespace boost::gil
Chris@16: 
Chris@16: #endif