ceph/src/boost/boost/gil/image_view.hpp

   1 //
   2 // Copyright 2005-2007 Adobe Systems Incorporated
   3 //
   4 // Distributed under the Boost Software License, Version 1.0
   5 // See accompanying file LICENSE_1_0.txt or copy at
   6 // http://www.boost.org/LICENSE_1_0.txt
   7 //
   8 #ifndef BOOST_GIL_IMAGE_VIEW_HPP
   9 #define BOOST_GIL_IMAGE_VIEW_HPP
  10
  11 #include <boost/gil/dynamic_step.hpp>
  12 #include <boost/gil/iterator_from_2d.hpp>
  13
  14 #include <boost/assert.hpp>
  15
  16 #include <cstddef>
  17 #include <iterator>
  18
  19 namespace boost { namespace gil {
  20
  21 ////////////////////////////////////////////////////////////////////////////////////////
  22 /// \class image_view
  23 /// \ingroup ImageViewModel PixelBasedModel
  24 /// \brief A lightweight object that interprets memory as a 2D array of pixels. Models ImageViewConcept,PixelBasedConcept,HasDynamicXStepTypeConcept,HasDynamicYStepTypeConcept,HasTransposedTypeConcept
  25 ///
  26 /// Image view consists of a pixel 2D locator (defining the mechanism for navigating in 2D)
  27 /// and the image dimensions.
  28 ///
  29 /// Image views to images are what ranges are to STL containers. They are lightweight objects,
  30 /// that don't own the pixels. It is the user's responsibility that the underlying data remains
  31 /// valid for the lifetime of the image view.
  32 ///
  33 /// Similar to iterators and ranges, constness of views does not extend to constness of pixels.
  34 /// A const \p image_view does not allow changing its location in memory (resizing, moving) but does
  35 /// not prevent one from changing the pixels. The latter requires an image view whose value_type
  36 /// is const.
  37 ///
  38 /// Images have interfaces consistent with STL 1D random access containers, so they can be used
  39 /// directly in STL algorithms like:
  40 /// \code
  41 ///  std::fill(img.begin(), img.end(), red_pixel);
  42 /// \endcode
  43 ///
  44 /// In addition, horizontal, vertical and 2D random access iterators are provided.
  45 ///
  46 /// Note also that \p image_view does not require that its element type be a pixel. It could be
  47 /// instantiated with a locator whose \p value_type models only \p Regular. In this case the image
  48 /// view models the weaker RandomAccess2DImageViewConcept, and does not model PixelBasedConcept.
  49 /// Many generic algorithms don't require the elements to be pixels.
  50 ///
  51 ////////////////////////////////////////////////////////////////////////////////////////
  52 template <typename Loc>     // Models 2D Pixel Locator
  53 class image_view
  54 {
  55 public:
  56     // aliases required by ConstRandomAccessNDImageViewConcept
  57     static const std::size_t num_dimensions=2;
  58     using value_type = typename Loc::value_type;
  59     using reference = typename Loc::reference;       // result of dereferencing
  60     using coord_t = typename Loc::coord_t;      // 1D difference type (same for all dimensions)
  61     using difference_type = coord_t; // result of operator-(1d_iterator,1d_iterator)
  62     using point_t = typename Loc::point_t;
  63     using locator = Loc;
  64     using const_t = image_view<typename Loc::const_t>;      // same as this type, but over const values
  65     template <std::size_t D> struct axis
  66     {
  67         using coord_t = typename Loc::template axis<D>::coord_t; // difference_type along each dimension
  68         using iterator = typename Loc::template axis<D>::iterator; // 1D iterator type along each dimension
  69     };
  70     using iterator = iterator_from_2d<Loc>;       // 1D iterator type for each pixel left-to-right inside top-to-bottom
  71     using const_iterator = typename const_t::iterator;  // may be used to examine, but not to modify values
  72     using const_reference = typename const_t::reference; // behaves as a const reference
  73     using pointer = typename std::iterator_traits<iterator>::pointer; // behaves as a pointer to the value type
  74     using reverse_iterator = std::reverse_iterator<iterator>;
  75     using size_type = std::size_t;
  76
  77     // aliases required by ConstRandomAccess2DImageViewConcept
  78     using xy_locator = locator;
  79     using x_iterator = typename xy_locator::x_iterator;     // pixel iterator along a row
  80     using y_iterator = typename xy_locator::y_iterator;     // pixel iterator along a column
  81     using x_coord_t = typename xy_locator::x_coord_t;
  82     using y_coord_t = typename xy_locator::y_coord_t;
  83
  84     template <typename Deref>
  85     struct add_deref
  86     {
  87         using type = image_view<typename Loc::template add_deref<Deref>::type>;
  88         static type make(image_view<Loc> const& view, Deref const& d)
  89         {
  90             return type(view.dimensions(), Loc::template add_deref<Deref>::make(view.pixels(), d));
  91         }
  92     };
  93
  94     image_view() : _dimensions(0,0) {}
  95     image_view(image_view const& img_view)
  96         : _dimensions(img_view.dimensions()), _pixels(img_view.pixels())
  97     {}
  98
  99     template <typename View>
 100     image_view(View const& view) : _dimensions(view.dimensions()), _pixels(view.pixels()) {}
 101
 102     template <typename L2>
 103     image_view(point_t const& dims, L2 const& loc) : _dimensions(dims), _pixels(loc) {}
 104
 105     template <typename L2>
 106     image_view(coord_t width, coord_t height, L2 const& loc)
 107         : _dimensions(x_coord_t(width), y_coord_t(height)), _pixels(loc)
 108     {}
 109
 110     template <typename View>
 111     image_view& operator=(View const& view)
 112     {
 113         _pixels = view.pixels();
 114         _dimensions = view.dimensions();
 115         return *this;
 116     }
 117
 118     image_view& operator=(image_view const& view)
 119     {
 120         // TODO: Self-assignment protection?
 121         _pixels = view.pixels();
 122         _dimensions = view.dimensions();
 123         return *this;
 124     }
 125
 126     template <typename View>
 127     bool operator==(View const &view) const
 128     {
 129         return pixels() == view.pixels() && dimensions() == view.dimensions();
 130     }
 131
 132     template <typename View>
 133     bool operator!=(View const& view) const
 134     {
 135         return !(*this == view);
 136     }
 137
 138     template <typename L2>
 139     friend void swap(image_view<L2> &lhs, image_view<L2> &rhs);
 140
 141     /// \brief Exchanges the elements of the current view with those of \a other
 142     ///       in constant time.
 143     ///
 144     /// \note Required by the Collection concept
 145     /// \see  https://www.boost.org/libs/utility/Collection.html
 146     void swap(image_view<Loc>& other)
 147     {
 148         using boost::gil::swap;
 149         swap(*this, other);
 150     }
 151
 152     auto dimensions() const -> point_t const&
 153     {
 154         return _dimensions;
 155     }
 156
 157     auto pixels() const -> locator const&
 158     {
 159         return _pixels;
 160     }
 161
 162     auto width() const -> x_coord_t
 163     {
 164         return dimensions().x;
 165     }
 166
 167     auto height() const -> y_coord_t
 168     {
 169         return dimensions().y;
 170     }
 171
 172     auto num_channels() const -> std::size_t
 173     {
 174         return gil::num_channels<value_type>::value;
 175     }
 176
 177     bool is_1d_traversable() const
 178     {
 179         return _pixels.is_1d_traversable(width());
 180     }
 181
 182     /// \brief Returns true if the view has no elements, false otherwise.
 183     ///
 184     /// \note Required by the Collection concept
 185     /// \see  https://www.boost.org/libs/utility/Collection.html
 186     bool empty() const
 187     {
 188         return !(width() > 0 && height() > 0);
 189     }
 190
 191     /// \brief Returns a reference to the first element in raster order.
 192     ///
 193     /// \note Required by the ForwardCollection, since view model the concept.
 194     /// \see  https://www.boost.org/libs/utility/Collection.html
 195     auto front() const -> reference
 196     {
 197         BOOST_ASSERT(!empty());
 198         return *begin();
 199     }
 200
 201     /// \brief Returns a reference to the last element in raster order.
 202     ///
 203     /// \note Required by the ForwardCollection, since view model the concept.
 204     /// \see  https://www.boost.org/libs/utility/Collection.html
 205     auto back() const -> reference
 206     {
 207         BOOST_ASSERT(!empty());
 208         return *rbegin();
 209     }
 210
 211     //\{@
 212     /// \name 1D navigation
 213     auto size() const -> size_type
 214     {
 215         return width() * height();
 216     }
 217
 218     auto begin() const -> iterator
 219     {
 220         return iterator(_pixels, _dimensions.x);
 221     }
 222
 223     auto end() const -> iterator
 224     {
 225         // potential performance problem!
 226         return begin() + static_cast<difference_type>(size());
 227     }
 228
 229     auto rbegin() const -> reverse_iterator
 230     {
 231         return reverse_iterator(end());
 232     }
 233
 234     auto rend() const -> reverse_iterator
 235     {
 236         return reverse_iterator(begin());
 237     }
 238
 239     auto operator[](difference_type i) const -> reference
 240     {
 241         BOOST_ASSERT(i < static_cast<difference_type>(size()));
 242         return begin()[i]; // potential performance problem!
 243     }
 244
 245     auto at(difference_type i) const ->iterator
 246     {
 247         BOOST_ASSERT(i < size());
 248         return begin() + i;
 249     }
 250
 251     auto at(point_t const& p) const -> iterator
 252     {
 253         BOOST_ASSERT(0 <= p.x && p.x < width());
 254         BOOST_ASSERT(0 <= p.y && p.y < height());
 255         return begin() + p.y * width() + p.x;
 256     }
 257
 258     auto at(x_coord_t x, y_coord_t y) const -> iterator
 259     {
 260         BOOST_ASSERT(0 <= x && x < width());
 261         BOOST_ASSERT(0 <= y && y < height());
 262         return begin() + y * width() + x;
 263     }
 264     //\}@
 265
 266     //\{@
 267     /// \name 2-D navigation
 268     auto operator()(point_t const& p) const -> reference
 269     {
 270         BOOST_ASSERT(0 <= p.x && p.x < width());
 271         BOOST_ASSERT(0 <= p.y && p.y < height());
 272         return _pixels(p.x, p.y);
 273     }
 274
 275     auto operator()(x_coord_t x, y_coord_t y) const -> reference
 276     {
 277         BOOST_ASSERT(0 <= x && x < width());
 278         BOOST_ASSERT(0 <= y && y < height());
 279         return _pixels(x, y);
 280     }
 281
 282     template <std::size_t D>
 283     auto axis_iterator(point_t const& p) const -> typename axis<D>::iterator
 284     {
 285         // allow request for iterators from inclusive range of [begin, end]
 286         BOOST_ASSERT(0 <= p.x && p.x <= width());
 287         BOOST_ASSERT(0 <= p.y && p.y <= height());
 288         return _pixels.template axis_iterator<D>(p);
 289     }
 290
 291     auto xy_at(x_coord_t x, y_coord_t y) const -> xy_locator
 292     {
 293         // TODO: Are relative locations of neighbors with negative offsets valid? Sampling?
 294         BOOST_ASSERT(x < width());
 295         BOOST_ASSERT(y < height());
 296         return _pixels + point_t(x, y);
 297     }
 298
 299     auto xy_at(point_t const& p) const -> locator
 300     {
 301         // TODO: Are relative locations of neighbors with negative offsets valid? Sampling?
 302         BOOST_ASSERT(p.x < width());
 303         BOOST_ASSERT(p.y < height());
 304         return _pixels + p;
 305     }
 306     //\}@
 307
 308     //\{@
 309     /// \name X navigation
 310     auto x_at(x_coord_t x, y_coord_t y) const -> x_iterator
 311     {
 312         BOOST_ASSERT(0 <= x && x <= width()); // allow request for [begin, end] inclusive
 313         BOOST_ASSERT(0 <= y && y < height());
 314         return _pixels.x_at(x, y);
 315     }
 316
 317     auto x_at(point_t const& p) const -> x_iterator
 318     {
 319         BOOST_ASSERT(0 <= p.x && p.x <= width()); // allow request for [begin, end] inclusive
 320         BOOST_ASSERT(0 <= p.y && p.y < height());
 321         return _pixels.x_at(p);
 322     }
 323
 324     auto row_begin(y_coord_t y) const -> x_iterator
 325     {
 326         BOOST_ASSERT(0 <= y && y < height());
 327         return x_at(0, y);
 328     }
 329
 330     auto row_end(y_coord_t y) const -> x_iterator
 331     {
 332         BOOST_ASSERT(0 <= y && y < height());
 333         return x_at(width(), y);
 334     }
 335     //\}@
 336
 337     //\{@
 338     /// \name Y navigation
 339     auto y_at(x_coord_t x, y_coord_t y) const -> y_iterator
 340     {
 341         BOOST_ASSERT(0 <= x && x < width());
 342         BOOST_ASSERT(0 <= y && y <= height()); // allow request for [begin, end] inclusive
 343         return xy_at(x, y).y();
 344     }
 345
 346     auto y_at(point_t const& p) const -> y_iterator
 347     {
 348         BOOST_ASSERT(0 <= p.x && p.x < width());
 349         BOOST_ASSERT(0 <= p.y && p.y <= height()); // allow request for [begin, end] inclusive
 350         return xy_at(p).y();
 351     }
 352
 353     auto col_begin(x_coord_t x) const -> y_iterator
 354     {
 355         BOOST_ASSERT(0 <= x && x < width());
 356         return y_at(x, 0);
 357     }
 358
 359     auto col_end(x_coord_t x) const -> y_iterator
 360     {
 361         BOOST_ASSERT(0 <= x && x < width());
 362         return y_at(x, height());
 363     }
 364     //\}@
 365
 366 private:
 367     template <typename L2>
 368     friend class image_view;
 369
 370     point_t    _dimensions;
 371     xy_locator _pixels;
 372 };
 373
 374 template <typename L2>
 375 inline void swap(image_view<L2>& x, image_view<L2>& y) {
 376     using std::swap;
 377     swap(x._dimensions,y._dimensions);
 378     swap(x._pixels, y._pixels);            // TODO: Extend further
 379 }
 380
 381 /////////////////////////////
 382 //  PixelBasedConcept
 383 /////////////////////////////
 384
 385 template <typename L>
 386 struct channel_type<image_view<L> > : public channel_type<L> {};
 387
 388 template <typename L>
 389 struct color_space_type<image_view<L> > : public color_space_type<L> {};
 390
 391 template <typename L>
 392 struct channel_mapping_type<image_view<L> > : public channel_mapping_type<L> {};
 393
 394 template <typename L>
 395 struct is_planar<image_view<L> > : public is_planar<L> {};
 396
 397 /////////////////////////////
 398 //  HasDynamicXStepTypeConcept
 399 /////////////////////////////
 400
 401 template <typename L>
 402 struct dynamic_x_step_type<image_view<L>>
 403 {
 404     using type = image_view<typename gil::dynamic_x_step_type<L>::type>;
 405 };
 406
 407 /////////////////////////////
 408 //  HasDynamicYStepTypeConcept
 409 /////////////////////////////
 410
 411 template <typename L>
 412 struct dynamic_y_step_type<image_view<L>>
 413 {
 414     using type = image_view<typename gil::dynamic_y_step_type<L>::type>;
 415 };
 416
 417 /////////////////////////////
 418 //  HasTransposedTypeConcept
 419 /////////////////////////////
 420
 421 template <typename L>
 422 struct transposed_type<image_view<L>>
 423 {
 424     using type = image_view<typename transposed_type<L>::type>;
 425 };
 426
 427 }}  // namespace boost::gil
 428
 429 #endif