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# bit_aligned_pixel_reference.hpp

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    00001 /*
    00002     Copyright 2005-2007 Adobe Systems Incorporated
    00003
    00004     Use, modification and distribution are subject to the Boost Software License,
    00005     Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
    00006     http://www.boost.org/LICENSE_1_0.txt).
    00007
    00008     See http://stlab.adobe.com/gil for most recent version including documentation.
    00009 */
    00010
    00011 /*************************************************************************************************/
    00012
    00013 #ifndef GIL_BIT_ALIGNED_PIXEL_REFERENCE_HPP
    00014 #define GIL_BIT_ALIGNED_PIXEL_REFERENCE_HPP
    00015
    00024
    00025 #include <functional>
    00026 #include <boost/mpl/accumulate.hpp>
    00027 #include <boost/mpl/at.hpp>
    00028 #include <boost/mpl/bool.hpp>
    00029 #include <boost/mpl/if.hpp>
    00030 #include <boost/mpl/plus.hpp>
    00031 #include <boost/mpl/push_back.hpp>
    00032 #include <boost/mpl/vector.hpp>
    00033 #include "gil_config.hpp"
    00034 #include "pixel.hpp"
    00035 #include "channel.hpp"
    00036
    00037 namespace boost { namespace gil {
    00038
    00040 //  bit_range
    00041 //
    00042 //  Represents a range of bits that can span multiple consecutive bytes. The range has a size fixed at compile time, but the offset is specified at run time.
    00044
    00045 template <int RangeSize, bool Mutable>
    00046 class bit_range {
    00047 public:
    00048     typedef typename mpl::if_c<Mutable,unsigned char,const unsigned char>::type byte_t;
    00049     typedef std::ptrdiff_t difference_type;
    00050     template <int RS, bool M> friend class bit_range;
    00051 private:
    00052     byte_t* _current_byte;   // the starting byte of the bit range
    00053     int     _bit_offset;     // offset from the beginning of the current byte. 0<=_bit_offset<=7
    00054
    00055 public:
    00056     bit_range() : _current_byte(NULL), _bit_offset(0) {}
    00057     bit_range(byte_t* current_byte, int bit_offset) : _current_byte(current_byte), _bit_offset(bit_offset) { assert(bit_offset>=0 && bit_offset<8); }
    00058
    00059     bit_range(const bit_range& br) : _current_byte(br._current_byte), _bit_offset(br._bit_offset) {}
    00060     template <bool M> bit_range(const bit_range<RangeSize,M>& br) : _current_byte(br._current_byte), _bit_offset(br._bit_offset) {}
    00061
    00062     bit_range& operator=(const bit_range& br) { _current_byte = br._current_byte; _bit_offset=br._bit_offset; return *this; }
    00063     bool operator==(const bit_range& br) const { return  _current_byte==br._current_byte && _bit_offset==br._bit_offset; }
    00064
    00065     bit_range& operator++() {
    00066         _current_byte += (_bit_offset+RangeSize) / 8;
    00067         _bit_offset    = (_bit_offset+RangeSize) % 8;
    00068         return *this;
    00069     }
    00070     bit_range& operator--() { bit_advance(-RangeSize); return *this; }
    00071
    00072     void bit_advance(difference_type num_bits) {
    00073         int new_offset = int(_bit_offset+num_bits);
    00074         _current_byte += new_offset / 8;
    00075         _bit_offset    = new_offset % 8;
    00076         if (_bit_offset<0) {
    00077             _bit_offset+=8;
    00078             --_current_byte;
    00079         }
    00080     }
    00081     difference_type bit_distance_to(const bit_range& b) const {
    00082         return (b.current_byte() - current_byte())*8 + b.bit_offset()-bit_offset();
    00083     }
    00084     byte_t* current_byte() const { return _current_byte; }
    00085     int     bit_offset()   const { return _bit_offset; }
    00086 };
    00087
    00088
    00092
    00116
    00117
    00118 template <typename BitField,
    00119           typename ChannelBitSizes,  // MPL integral vector defining the number of bits for each channel. For example, for 565RGB, vector_c<int,5,6,5>
    00120           typename Layout,
    00121           bool IsMutable>
    00122 struct bit_aligned_pixel_reference {
    00123     BOOST_STATIC_CONSTANT(int, bit_size = (mpl::accumulate<ChannelBitSizes, mpl::int_<0>, mpl::plus<mpl::_1, mpl::_2> >::type::value));
    00124     typedef boost::gil::bit_range<bit_size,IsMutable>                                           bit_range_t;
    00125     typedef BitField                                                                bitfield_t;
    00126     typedef typename mpl::if_c<IsMutable,unsigned char*,const unsigned char*>::type data_ptr_t;
    00127
    00128     typedef Layout layout_t;
    00129
    00130     typedef typename packed_pixel_type<bitfield_t,ChannelBitSizes,Layout>::type       value_type;
    00131     typedef const bit_aligned_pixel_reference                                         reference;
    00132     typedef const bit_aligned_pixel_reference<BitField,ChannelBitSizes,Layout,false>  const_reference;
    00133
    00134     BOOST_STATIC_CONSTANT(bool, is_mutable = IsMutable);
    00135
    00136     bit_aligned_pixel_reference(){}
    00137     bit_aligned_pixel_reference(data_ptr_t data_ptr, int bit_offset)   : _bit_range(data_ptr, bit_offset) {}
    00138     explicit bit_aligned_pixel_reference(const bit_range_t& bit_range) : _bit_range(bit_range) {}
    00139     template <bool IsMutable2> bit_aligned_pixel_reference(const bit_aligned_pixel_reference<BitField,ChannelBitSizes,Layout,IsMutable2>& p) : _bit_range(p._bit_range) {}
    00140
    00141     // Grayscale references can be constructed from the channel reference
    00142     explicit bit_aligned_pixel_reference(const typename kth_element_type<bit_aligned_pixel_reference,0>::type channel0) : _bit_range(static_cast<data_ptr_t>(&channel0), channel0.first_bit()) {
    00143         BOOST_STATIC_ASSERT((num_channels<bit_aligned_pixel_reference>::value==1));
    00144     }
    00145
    00146     // Construct from another compatible pixel type
    00147     bit_aligned_pixel_reference(const bit_aligned_pixel_reference& p) : _bit_range(p._bit_range) {}
    00148     template <typename BF, typename CR> bit_aligned_pixel_reference(packed_pixel<BF,CR,Layout>& p) : _bit_range(static_cast<data_ptr_t>(&at_c<0>(p)), at_c<0>(p).first_bit()) {
    00149         check_compatible<packed_pixel<BF,CR,Layout> >();
    00150     }
    00151
    00152     const bit_aligned_pixel_reference& operator=(const bit_aligned_pixel_reference& p) const { static_copy(p,*this); return *this; }
    00153     template <typename P> const bit_aligned_pixel_reference& operator=(const P& p) const { assign(p, mpl::bool_<is_pixel<P>::value>()); return *this; }
    00154
    00155     template <typename P> bool operator==(const P& p) const { return equal(p, mpl::bool_<is_pixel<P>::value>()); }
    00156     template <typename P> bool operator!=(const P& p) const { return !(*this==p); }
    00157
    00158     const bit_aligned_pixel_reference* operator->()    const { return this; }
    00159
    00160     const bit_range_t& bit_range() const { return _bit_range; }
    00161 private:
    00162     mutable bit_range_t _bit_range;
    00163     template <typename B, typename C, typename L, bool M> friend struct bit_aligned_pixel_reference;
    00164
    00165     template <typename Pixel> static void check_compatible() { gil_function_requires<PixelsCompatibleConcept<Pixel,bit_aligned_pixel_reference> >(); }
    00166
    00167     template <typename Pixel> void assign(const Pixel& p, mpl::true_) const { check_compatible<Pixel>(); static_copy(p,*this); }
    00168     template <typename Pixel> bool  equal(const Pixel& p, mpl::true_) const { check_compatible<Pixel>(); return static_equal(*this,p); }
    00169
    00170 private:
    00171     static void check_gray() {  BOOST_STATIC_ASSERT((is_same<typename Layout::color_space_t, gray_t>::value)); }
    00172     template <typename Channel> void assign(const Channel& chan, mpl::false_) const { check_gray(); at_c<0>(*this)=chan; }
    00173     template <typename Channel> bool equal (const Channel& chan, mpl::false_) const { check_gray(); return at_c<0>(*this)==chan; }
    00174 };
    00175
    00177 //  ColorBasedConcept
    00179
    00180 template <typename BitField, typename ChannelBitSizes, typename L, bool IsMutable, int K>
    00181 struct kth_element_type<bit_aligned_pixel_reference<BitField,ChannelBitSizes,L,IsMutable>, K> {
    00182 public:
    00183     typedef const packed_dynamic_channel_reference<BitField, mpl::at_c<ChannelBitSizes,K>::type::value, IsMutable> type;
    00184 };
    00185
    00186 template <typename B, typename C, typename L, bool M, int K>
    00187 struct kth_element_reference_type<bit_aligned_pixel_reference<B,C,L,M>, K>
    00188     : public kth_element_type<bit_aligned_pixel_reference<B,C,L,M>, K> {};
    00189
    00190 template <typename B, typename C, typename L, bool M, int K>
    00191 struct kth_element_const_reference_type<bit_aligned_pixel_reference<B,C,L,M>, K>
    00192     : public kth_element_type<bit_aligned_pixel_reference<B,C,L,M>, K> {};
    00193
    00194
    00195 namespace detail {
    00196     // returns sum of IntegralVector[0] ... IntegralVector[K-1]
    00197     template <typename IntegralVector, int K>
    00198     struct sum_k : public mpl::plus<sum_k<IntegralVector,K-1>, typename mpl::at_c<IntegralVector,K-1>::type > {};
    00199
    00200     template <typename IntegralVector> struct sum_k<IntegralVector,0> : public mpl::int_<0> {};
    00201 }
    00202
    00203 // at_c required by MutableColorBaseConcept
    00204 template <int K, typename BitField, typename ChannelBitSizes, typename L, bool Mutable> inline
    00205 typename kth_element_reference_type<bit_aligned_pixel_reference<BitField,ChannelBitSizes,L,Mutable>,K>::type
    00206 at_c(const bit_aligned_pixel_reference<BitField,ChannelBitSizes,L,Mutable>& p) {
    00207     typedef bit_aligned_pixel_reference<BitField,ChannelBitSizes,L,Mutable> pixel_t;
    00208     typedef typename kth_element_reference_type<pixel_t,K>::type channel_t;
    00209     typedef typename pixel_t::bit_range_t bit_range_t;
    00210
    00211     bit_range_t bit_range(p.bit_range());
    00212     bit_range.bit_advance(detail::sum_k<ChannelBitSizes,K>::value);
    00213
    00214     return channel_t(bit_range.current_byte(), bit_range.bit_offset());
    00215 }
    00216
    00218 //  PixelConcept
    00220
    00222 template <typename B, typename C, typename L, bool M>
    00223 struct is_pixel<bit_aligned_pixel_reference<B,C,L,M> > : public mpl::true_{};
    00224
    00226 //  PixelBasedConcept
    00228
    00229 template <typename B, typename C, typename L, bool M>
    00230 struct color_space_type<bit_aligned_pixel_reference<B,C,L,M> > {
    00231     typedef typename L::color_space_t type;
    00232 };
    00233
    00234 template <typename B, typename C, typename L, bool M>
    00235 struct channel_mapping_type<bit_aligned_pixel_reference<B,C,L,M> > {
    00236     typedef typename L::channel_mapping_t type;
    00237 };
    00238
    00239 template <typename B, typename C, typename L, bool M>
    00240 struct is_planar<bit_aligned_pixel_reference<B,C,L,M> > : mpl::false_ {};
    00241
    00243 //  pixel_reference_type
    00245
    00246 namespace detail {
    00247     // returns a vector containing K copies of the type T
    00248     template <unsigned K, typename T> struct k_copies;
    00249     template <typename T> struct k_copies<0,T> {
    00250         typedef mpl::vector0<> type;
    00251     };
    00252     template <unsigned K, typename T> struct k_copies : public mpl::push_back<typename k_copies<K-1,T>::type, T> {};
    00253 }
    00254
    00255 // Constructs a homogeneous bit_aligned_pixel_reference given a channel reference
    00256 template <typename BitField, int NumBits, typename Layout>
    00257 struct pixel_reference_type<const packed_dynamic_channel_reference<BitField,NumBits,false>, Layout, false, false> {
    00258 private:
    00259     typedef typename mpl::size<typename Layout::color_space_t>::type size_t;
    00260     typedef typename detail::k_copies<size_t::value,mpl::integral_c<unsigned,NumBits> >::type channel_bit_sizes_t;
    00261 public:
    00262     typedef bit_aligned_pixel_reference<BitField, channel_bit_sizes_t, Layout, false> type;
    00263 };
    00264
    00265 // Same but for the mutable case. We cannot combine the mutable and read-only cases because this triggers ambiguity
    00266 template <typename BitField, int NumBits, typename Layout>
    00267 struct pixel_reference_type<const packed_dynamic_channel_reference<BitField,NumBits,true>, Layout, false, true> {
    00268 private:
    00269     typedef typename mpl::size<typename Layout::color_space_t>::type size_t;
    00270     typedef typename detail::k_copies<size_t::value,mpl::integral_c<unsigned,NumBits> >::type channel_bit_sizes_t;
    00271 public:
    00272     typedef bit_aligned_pixel_reference<BitField, channel_bit_sizes_t, Layout, true> type;
    00273 };
    00274
    00275 } }  // namespace boost::gil
    00276
    00277 namespace std {
    00278 // We are forced to define swap inside std namespace because on some platforms (Visual Studio 8) STL calls swap qualified.
    00279 // swap with 'left bias':
    00280 // - swap between proxy and anything
    00281 // - swap between value type and proxy
    00282 // - swap between proxy and proxy
    00283 // Having three overloads allows us to swap between different (but compatible) models of PixelConcept
    00284
    00285 template <typename B, typename C, typename L, typename R> inline
    00286 void swap(const boost::gil::bit_aligned_pixel_reference<B,C,L,true> x, R& y) {
    00287     boost::gil::swap_proxy<typename boost::gil::bit_aligned_pixel_reference<B,C,L,true>::value_type>(x,y);
    00288 }
    00289
    00290
    00291 template <typename B, typename C, typename L> inline
    00292 void swap(typename boost::gil::bit_aligned_pixel_reference<B,C,L,true>::value_type& x, const boost::gil::bit_aligned_pixel_reference<B,C,L,true> y) {
    00293     boost::gil::swap_proxy<typename boost::gil::bit_aligned_pixel_reference<B,C,L,true>::value_type>(x,y);
    00294 }
    00295
    00296
    00297 template <typename B, typename C, typename L> inline
    00298 void swap(const boost::gil::bit_aligned_pixel_reference<B,C,L,true> x, const boost::gil::bit_aligned_pixel_reference<B,C,L,true> y) {
    00299     boost::gil::swap_proxy<typename boost::gil::bit_aligned_pixel_reference<B,C,L,true>::value_type>(x,y);
    00300 }
    00301 }   // namespace std
    00302 #endif