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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://opensource.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 ChannelBitSizes,  // MPL integral vector defining the number of bits for each channel. For example, for 565RGB, vector_c<int,5,6,5>
    00119           typename Layout,
    00120           bool IsMutable>
    00121 struct bit_aligned_pixel_reference {
    00122     BOOST_STATIC_CONSTANT(int, bit_size = (mpl::accumulate<ChannelBitSizes, mpl::int_<0>, mpl::plus<mpl::_1, mpl::_2> >::type::value));
    00123     typedef bit_range<bit_size,IsMutable>                                           bit_range_t;
    00124     typedef typename detail::min_fast_uint<bit_size>::type                          bitfield_t;
    00125     typedef typename mpl::if_c<IsMutable,unsigned char*,const unsigned char*>::type data_ptr_t;
    00126
    00127     typedef Layout layout_t;
    00128
    00129     typedef typename packed_pixel_type<bitfield_t,ChannelBitSizes,Layout>::type value_type;
    00130     typedef const bit_aligned_pixel_reference                                    reference;
    00131     typedef const bit_aligned_pixel_reference<ChannelBitSizes,Layout,false>      const_reference;
    00132
    00133     BOOST_STATIC_CONSTANT(bool, is_mutable = IsMutable);
    00134
    00135     bit_aligned_pixel_reference(){}
    00136     bit_aligned_pixel_reference(data_ptr_t data_ptr, int bit_offset)   : _bit_range(data_ptr, bit_offset) {}
    00137     explicit bit_aligned_pixel_reference(const bit_range_t& bit_range) : _bit_range(bit_range) {}
    00138     template <bool IsMutable2> bit_aligned_pixel_reference(const bit_aligned_pixel_reference<ChannelBitSizes,Layout,IsMutable2>& p) : _bit_range(p._bit_range) {}
    00139
    00140     // Grayscale references can be constructed from the channel reference
    00141     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()) {
    00142         BOOST_STATIC_ASSERT((num_channels<bit_aligned_pixel_reference>::value==1));
    00143     }
    00144
    00145     // Construct from another compatible pixel type
    00146     bit_aligned_pixel_reference(const bit_aligned_pixel_reference& p) : _bit_range(p._bit_range) {}
    00147     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()) {
    00148         check_compatible<packed_pixel<BF,CR,Layout> >();
    00149     }
    00150
    00151     template <typename P> const bit_aligned_pixel_reference& operator=(const P& p)    const { check_compatible<P>(); static_copy(p,*this); return *this; }
    00152     const bit_aligned_pixel_reference& operator=(const bit_aligned_pixel_reference& p) const { static_copy(p,*this); return *this; }
    00153
    00154     template <typename P> bool operator==(const P& p) const { check_compatible<P>(); return static_equal(*this,p); }
    00155     template <typename P> bool operator!=(const P& p) const { return !(*this==p); }
    00156
    00157     const bit_aligned_pixel_reference* operator->()    const { return this; }
    00158
    00159     const bit_range_t& bit_range() const { return _bit_range; }
    00160 private:
    00161     mutable bit_range_t _bit_range;
    00162     template <typename C, typename L, bool M> friend struct bit_aligned_pixel_reference;
    00163
    00164     template <typename Pixel> static void check_compatible() { gil_function_requires<PixelsCompatibleConcept<Pixel,bit_aligned_pixel_reference> >(); }
    00165 };
    00166
    00168 //  ColorBasedConcept
    00170
    00171 template <typename ChannelBitSizes, typename L, bool IsMutable, int K>
    00172 struct kth_element_type<bit_aligned_pixel_reference<ChannelBitSizes,L,IsMutable>, K> {
    00173 private:
    00174     typedef typename bit_aligned_pixel_reference<ChannelBitSizes,L,IsMutable>::bitfield_t bitfield_t;
    00175 public:
    00176     typedef const packed_dynamic_channel_reference<bitfield_t, mpl::at_c<ChannelBitSizes,K>::type::value, IsMutable> type;
    00177 };
    00178
    00179 template <typename C, typename L, bool M, int K>
    00180 struct kth_element_reference_type<bit_aligned_pixel_reference<C,L,M>, K>
    00181     : public kth_element_type<bit_aligned_pixel_reference<C,L,M>, K> {};
    00182
    00183 template <typename C, typename L, bool M, int K>
    00184 struct kth_element_const_reference_type<bit_aligned_pixel_reference<C,L,M>, K>
    00185     : public kth_element_type<bit_aligned_pixel_reference<C,L,M>, K> {};
    00186
    00187
    00188 namespace detail {
    00189     // returns sum of IntegralVector[0] ... IntegralVector[K-1]
    00190     template <typename IntegralVector, int K>
    00191     struct sum_k : public mpl::plus<sum_k<IntegralVector,K-1>, typename mpl::at_c<IntegralVector,K-1>::type > {};
    00192
    00193     template <typename IntegralVector> struct sum_k<IntegralVector,0> : public mpl::int_<0> {};
    00194 }
    00195
    00196 // at_c required by MutableColorBaseConcept
    00197 template <int K, typename ChannelBitSizes, typename L, bool Mutable> inline
    00198 typename kth_element_reference_type<bit_aligned_pixel_reference<ChannelBitSizes,L,Mutable>,K>::type
    00199 at_c(const bit_aligned_pixel_reference<ChannelBitSizes,L,Mutable>& p) {
    00200     typedef bit_aligned_pixel_reference<ChannelBitSizes,L,Mutable> pixel_t;
    00201     typedef typename kth_element_reference_type<pixel_t,K>::type channel_t;
    00202     typedef typename pixel_t::bit_range_t bit_range_t;
    00203
    00204     bit_range_t bit_range(p.bit_range());
    00205     bit_range.bit_advance(detail::sum_k<ChannelBitSizes,K>::value);
    00206
    00207     return channel_t(bit_range.current_byte(), bit_range.bit_offset());
    00208 }
    00209
    00211 //  PixelConcept
    00213
    00215 template <typename C, typename L, bool M>
    00216 struct is_pixel<bit_aligned_pixel_reference<C,L,M> > : public mpl::true_{};
    00217
    00219 //  PixelBasedConcept
    00221
    00222 template <typename C, typename L, bool M>
    00223 struct color_space_type<bit_aligned_pixel_reference<C,L,M> > {
    00224     typedef typename L::color_space_t type;
    00225 };
    00226
    00227 template <typename C, typename L, bool M>
    00228 struct channel_mapping_type<bit_aligned_pixel_reference<C,L,M> > {
    00229     typedef typename L::channel_mapping_t type;
    00230 };
    00231
    00232 template <typename C, typename L, bool M>
    00233 struct is_planar<bit_aligned_pixel_reference<C,L,M> > : mpl::false_ {};
    00234
    00236 //  pixel_reference_type
    00238
    00239 namespace detail {
    00240     // returns a vector containing K copies of the type T
    00241     template <unsigned K, typename T> struct k_copies;
    00242     template <typename T> struct k_copies<0,T> {
    00243         typedef mpl::vector0<> type;
    00244     };
    00245     template <unsigned K, typename T> struct k_copies : public mpl::push_back<typename k_copies<K-1,T>::type, T> {};
    00246 }
    00247
    00248 // Constructs a homogeneous bit_aligned_pixel_reference given a channel reference
    00249 // Note: BitField must be the same type as pixel_reference_type<...>::type::bitfield_t, but it is too complicated to ensure this
    00250 template <typename BitField, int NumBits, typename Layout>
    00251 struct pixel_reference_type<const packed_dynamic_channel_reference<BitField,NumBits,false>, Layout, false, false> {
    00252 private:
    00253     typedef typename mpl::size<typename Layout::color_space_t>::type size_t;
    00254     typedef typename detail::k_copies<size_t::value,mpl::integral_c<unsigned,NumBits> >::type channel_bit_sizes_t;
    00255 public:
    00256     typedef bit_aligned_pixel_reference<channel_bit_sizes_t, Layout, false> type;
    00257 };
    00258
    00259 // Same but for the mutable case. We cannot combine the mutable and read-only cases because this triggers ambiguity
    00260 // Note: BitField must be the same type as pixel_reference_type<...>::type::bitfield_t, but it is too complicated to ensure this
    00261 template <typename BitField, int NumBits, typename Layout>
    00262 struct pixel_reference_type<const packed_dynamic_channel_reference<BitField,NumBits,true>, Layout, false, true> {
    00263 private:
    00264     typedef typename mpl::size<typename Layout::color_space_t>::type size_t;
    00265     typedef typename detail::k_copies<size_t::value,mpl::integral_c<unsigned,NumBits> >::type channel_bit_sizes_t;
    00266 public:
    00267     typedef bit_aligned_pixel_reference<channel_bit_sizes_t, Layout, true> type;
    00268 };
    00269
    00270 } }  // namespace boost::gil
    00271
    00272 namespace std {
    00273 // We are forced to define swap inside std namespace because on some platforms (Visual Studio 8) STL calls swap qualified.
    00274 // swap with 'left bias':
    00275 // - swap between proxy and anything
    00276 // - swap between value type and proxy
    00277 // - swap between proxy and proxy
    00278 // Having three overloads allows us to swap between different (but compatible) models of PixelConcept
    00279
    00280 template <typename C, typename L, typename R> inline
    00281 void swap(boost::gil::bit_aligned_pixel_reference<C,L,true> x, R& y) {
    00282     boost::gil::swap_proxy<typename boost::gil::bit_aligned_pixel_reference<C,L,true>::value_type>(x,y);
    00283 }
    00284
    00285
    00286 template <typename C, typename L> inline
    00287 void swap(typename boost::gil::bit_aligned_pixel_reference<C,L,true>::value_type& x, boost::gil::bit_aligned_pixel_reference<C,L,true> y) {
    00288     boost::gil::swap_proxy<typename boost::gil::bit_aligned_pixel_reference<C,L,true>::value_type>(x,y);
    00289 }
    00290
    00291
    00292 template <typename C, typename L> inline
    00293 void swap(boost::gil::bit_aligned_pixel_reference<C,L,true> x, boost::gil::bit_aligned_pixel_reference<C,L,true> y) {
    00294     boost::gil::swap_proxy<typename boost::gil::bit_aligned_pixel_reference<C,L,true>::value_type>(x,y);
    00295 }
    00296 }   // namespace std
    00297 #endif