2 // Copyright 2005-2007 Adobe Systems Incorporated
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
8 #ifndef BOOST_GIL_CHANNEL_HPP
9 #define BOOST_GIL_CHANNEL_HPP
11 #include <boost/gil/utilities.hpp>
13 #include <boost/assert.hpp>
14 #include <boost/config.hpp>
15 #include <boost/config/pragma_message.hpp>
16 #include <boost/integer/integer_mask.hpp>
20 #include <type_traits>
22 #ifdef BOOST_GIL_DOXYGEN_ONLY
23 /// \def BOOST_GIL_CONFIG_HAS_UNALIGNED_ACCESS
24 /// \brief Define to allow unaligned memory access for models of packed channel value.
25 /// Theoretically (or historically?) on platforms which support dereferencing on
26 /// non-word memory boundary, unaligned access may result in performance improvement.
27 /// \warning Unfortunately, this optimization may be a C/C++ strict aliasing rules
28 /// violation, if accessed data buffer has effective type that cannot be aliased
29 /// without leading to undefined behaviour.
30 #define BOOST_GIL_CONFIG_HAS_UNALIGNED_ACCESS
33 #ifdef BOOST_GIL_CONFIG_HAS_UNALIGNED_ACCESS
34 #if defined(sun) || defined(__sun) || \ // SunOS
35 defined(__osf__) || defined(__osf) || \ // Tru64
36 defined(_hpux) || defined(hpux) || \ // HP-UX
37 defined(__arm__) || defined(__ARM_ARCH) || \ // ARM
39 #error Unaligned access strictly disabled for some UNIX platforms or ARM architecture
40 #elif defined(__i386__) || defined(__x86_64__) || defined(__vax__)
41 // The check for little-endian architectures that tolerate unaligned memory
42 // accesses is just an optimization. Nothing will break if it fails to detect
43 // a suitable architecture.
45 // Unfortunately, this optimization may be a C/C++ strict aliasing rules violation
46 // if accessed data buffer has effective type that cannot be aliased
47 // without leading to undefined behaviour.
48 BOOST_PRAGMA_MESSAGE("CAUTION: Unaligned access tolerated on little-endian may cause undefined behaviour")
50 #error Unaligned access disabled for unknown platforms and architectures
52 #endif // defined(BOOST_GIL_CONFIG_HAS_UNALIGNED_ACCESS)
54 namespace boost { namespace gil {
56 ///////////////////////////////////////////
59 //// \ingroup ChannelModel
60 //// \class channel_traits
61 //// \brief defines properties of channels, such as their range and associated types
63 //// The channel traits must be defined for every model of ChannelConcept
64 //// Default traits are provided. For built-in types the default traits use
65 //// built-in pointer and reference and the channel range is the physical
66 //// range of the type. For classes, the default traits forward the associated types
67 //// and range to the class.
69 ///////////////////////////////////////////
73 template <typename T, bool IsClass>
74 struct channel_traits_impl;
76 // channel traits for custom class
78 struct channel_traits_impl<T, true>
80 using value_type = typename T::value_type;
81 using reference = typename T::reference;
82 using pointer = typename T::pointer;
83 using const_reference = typename T::const_reference;
84 using const_pointer = typename T::const_pointer;
85 static constexpr bool is_mutable = T::is_mutable;
86 static value_type min_value() { return T::min_value(); }
87 static value_type max_value() { return T::max_value(); }
90 // channel traits implementation for built-in integral or floating point channel type
92 struct channel_traits_impl<T, false>
97 using const_reference = T const&;
98 using const_pointer = T const*;
99 static constexpr bool is_mutable = true;
100 static value_type min_value() { return (std::numeric_limits<T>::min)(); }
101 static value_type max_value() { return (std::numeric_limits<T>::max)(); }
104 // channel traits implementation for constant built-in scalar or floating point type
105 template <typename T>
106 struct channel_traits_impl<T const, false> : channel_traits_impl<T, false>
108 using reference = T const&;
109 using pointer = T const*;
110 static constexpr bool is_mutable = false;
113 } // namespace detail
116 \ingroup ChannelModel
117 \brief Traits for channels. Contains the following members:
119 template <typename Channel>
120 struct channel_traits {
121 using value_type = ...;
122 using reference = ...;
124 using const_reference = ...;
125 using const_pointer = ...;
127 static const bool is_mutable;
128 static value_type min_value();
129 static value_type max_value();
133 template <typename T>
134 struct channel_traits : detail::channel_traits_impl<T, std::is_class<T>::value> {};
136 // Channel traits for C++ reference type - remove the reference
137 template <typename T>
138 struct channel_traits<T&> : channel_traits<T> {};
140 // Channel traits for constant C++ reference type
141 template <typename T>
142 struct channel_traits<T const&> : channel_traits<T>
144 using reference = typename channel_traits<T>::const_reference;
145 using pointer = typename channel_traits<T>::const_pointer;
146 static constexpr bool is_mutable = false;
149 ///////////////////////////////////////////
150 //// scoped_channel_value
151 ///////////////////////////////////////////
153 /// \defgroup ScopedChannelValue scoped_channel_value
154 /// \ingroup ChannelModel
155 /// \brief A channel adaptor that modifies the range of the source channel. Models: ChannelValueConcept
159 /// // Create a double channel with range [-0.5 .. 0.5]
160 /// struct double_minus_half { static double apply() { return -0.5; } };
161 /// struct double_plus_half { static double apply() { return 0.5; } };
162 /// using bits64custom_t = scoped_channel_value<double, double_minus_half, double_plus_half>;
164 /// // channel_convert its maximum should map to the maximum
165 /// bits64custom_t x = channel_traits<bits64custom_t>::max_value();
166 /// assert(x == 0.5);
167 /// uint16_t y = channel_convert<uint16_t>(x);
168 /// assert(y == 65535);
171 /// \ingroup ScopedChannelValue
172 /// \brief A channel adaptor that modifies the range of the source channel. Models: ChannelValueConcept
173 /// \tparam BaseChannelValue base channel (models ChannelValueConcept)
174 /// \tparam MinVal class with a static apply() function returning the minimum channel values
175 /// \tparam MaxVal class with a static apply() function returning the maximum channel values
176 template <typename BaseChannelValue, typename MinVal, typename MaxVal>
177 struct scoped_channel_value
179 using value_type = scoped_channel_value<BaseChannelValue, MinVal, MaxVal>;
180 using reference = value_type&;
181 using pointer = value_type*;
182 using const_reference = value_type const&;
183 using const_pointer = value_type const*;
184 static constexpr bool is_mutable = channel_traits<BaseChannelValue>::is_mutable;
186 using base_channel_t = BaseChannelValue;
188 static value_type min_value() { return MinVal::apply(); }
189 static value_type max_value() { return MaxVal::apply(); }
191 scoped_channel_value() = default;
192 scoped_channel_value(scoped_channel_value const& other) : value_(other.value_) {}
193 scoped_channel_value& operator=(scoped_channel_value const& other) = default;
194 scoped_channel_value(BaseChannelValue value) : value_(value) {}
195 scoped_channel_value& operator=(BaseChannelValue value)
201 scoped_channel_value& operator++() { ++value_; return *this; }
202 scoped_channel_value& operator--() { --value_; return *this; }
204 scoped_channel_value operator++(int) { scoped_channel_value tmp=*this; this->operator++(); return tmp; }
205 scoped_channel_value operator--(int) { scoped_channel_value tmp=*this; this->operator--(); return tmp; }
207 template <typename Scalar2> scoped_channel_value& operator+=(Scalar2 v) { value_+=v; return *this; }
208 template <typename Scalar2> scoped_channel_value& operator-=(Scalar2 v) { value_-=v; return *this; }
209 template <typename Scalar2> scoped_channel_value& operator*=(Scalar2 v) { value_*=v; return *this; }
210 template <typename Scalar2> scoped_channel_value& operator/=(Scalar2 v) { value_/=v; return *this; }
212 operator BaseChannelValue() const { return value_; }
214 BaseChannelValue value_{};
217 template <typename T>
218 struct float_point_zero
220 static constexpr T apply() { return 0.0f; }
223 template <typename T>
224 struct float_point_one
226 static constexpr T apply() { return 1.0f; }
229 ///////////////////////////////////////////
230 //// Support for sub-byte channels. These are integral channels whose value is contained in a range of bits inside an integral type
231 ///////////////////////////////////////////
233 // It is necessary for packed channels to have their own value type. They cannot simply use an integral large enough to store the data. Here is why:
234 // - Any operation that requires returning the result by value will otherwise return the built-in integral type, which will have incorrect range
235 // That means that after getting the value of the channel we cannot properly do channel_convert, channel_invert, etc.
236 // - Two channels are declared compatible if they have the same value type. That means that a packed channel is incorrectly declared compatible with an integral type
239 // returns the smallest fast unsigned integral type that has at least NumBits bits
240 template <int NumBits>
241 struct min_fast_uint :
246 typename std::conditional
250 typename std::conditional
260 template <int NumBits>
262 : std::conditional<NumBits < 32, std::uint32_t, std::uint64_t>
265 template <int NumBits>
267 : std::conditional<NumBits <= 32, std::uint32_t, std::uint64_t>
270 } // namespace detail
272 /// \defgroup PackedChannelValueModel packed_channel_value
273 /// \ingroup ChannelModel
274 /// \brief Represents the value of an unsigned integral channel operating over a bit range. Models: ChannelValueConcept
277 /// // A 4-bit unsigned integral channel.
278 /// using bits4 = packed_channel_value<4>;
280 /// assert(channel_traits<bits4>::min_value()==0);
281 /// assert(channel_traits<bits4>::max_value()==15);
282 /// assert(sizeof(bits4)==1);
283 /// static_assert(gil::is_channel_integral<bits4>::value, "");
286 /// \ingroup PackedChannelValueModel
287 /// \brief The value of a subbyte channel. Models: ChannelValueConcept
288 template <int NumBits>
289 class packed_channel_value
292 using integer_t = typename detail::min_fast_uint<NumBits>::type;
294 using value_type = packed_channel_value<NumBits>;
295 using reference = value_type&;
296 using const_reference = value_type const&;
297 using pointer = value_type*;
298 using const_pointer = value_type const*;
299 static constexpr bool is_mutable = true;
301 static value_type min_value() { return 0; }
302 static value_type max_value() { return low_bits_mask_t< NumBits >::sig_bits; }
304 packed_channel_value() = default;
305 packed_channel_value(integer_t v)
307 value_ = static_cast<integer_t>(v & low_bits_mask_t<NumBits>::sig_bits_fast);
310 template <typename Scalar>
311 packed_channel_value(Scalar v)
313 value_ = packed_channel_value(static_cast<integer_t>(v));
316 static unsigned int num_bits() { return NumBits; }
318 operator integer_t() const { return value_; }
326 template <std::size_t K>
327 struct static_copy_bytes
329 void operator()(unsigned char const* from, unsigned char* to) const
332 static_copy_bytes<K - 1>()(++from, ++to);
337 struct static_copy_bytes<0>
339 void operator()(unsigned char const*, unsigned char*) const {}
342 template <typename Derived, typename BitField, int NumBits, bool IsMutable>
343 class packed_channel_reference_base
346 using data_ptr_t = typename std::conditional<IsMutable, void*, void const*>::type;
348 data_ptr_t _data_ptr; // void* pointer to the first byte of the bit range
350 using value_type = packed_channel_value<NumBits>;
351 using reference = const Derived;
352 using pointer = value_type *;
353 using const_pointer = const value_type *;
354 static constexpr int num_bits = NumBits;
355 static constexpr bool is_mutable = IsMutable;
357 static value_type min_value() { return channel_traits<value_type>::min_value(); }
358 static value_type max_value() { return channel_traits<value_type>::max_value(); }
360 using bitfield_t = BitField;
361 using integer_t = typename value_type::integer_t;
363 packed_channel_reference_base(data_ptr_t data_ptr) : _data_ptr(data_ptr) {}
364 packed_channel_reference_base(const packed_channel_reference_base& ref) : _data_ptr(ref._data_ptr) {}
365 const Derived& operator=(integer_t v) const { set(v); return derived(); }
367 const Derived& operator++() const { set(get()+1); return derived(); }
368 const Derived& operator--() const { set(get()-1); return derived(); }
370 Derived operator++(int) const { Derived tmp=derived(); this->operator++(); return tmp; }
371 Derived operator--(int) const { Derived tmp=derived(); this->operator--(); return tmp; }
373 template <typename Scalar2> const Derived& operator+=(Scalar2 v) const { set( static_cast<integer_t>( get() + v )); return derived(); }
374 template <typename Scalar2> const Derived& operator-=(Scalar2 v) const { set( static_cast<integer_t>( get() - v )); return derived(); }
375 template <typename Scalar2> const Derived& operator*=(Scalar2 v) const { set( static_cast<integer_t>( get() * v )); return derived(); }
376 template <typename Scalar2> const Derived& operator/=(Scalar2 v) const { set( static_cast<integer_t>( get() / v )); return derived(); }
378 operator integer_t() const { return get(); }
379 data_ptr_t operator &() const {return _data_ptr;}
382 using num_value_t = typename detail::num_value_fn<NumBits>::type;
383 using max_value_t = typename detail::max_value_fn<NumBits>::type;
385 static const num_value_t num_values = static_cast< num_value_t >( 1 ) << NumBits ;
386 static const max_value_t max_val = static_cast< max_value_t >( num_values - 1 );
388 #if defined(BOOST_GIL_CONFIG_HAS_UNALIGNED_ACCESS)
389 const bitfield_t& get_data() const { return *static_cast<const bitfield_t*>(_data_ptr); }
390 void set_data(const bitfield_t& val) const { *static_cast< bitfield_t*>(_data_ptr) = val; }
392 bitfield_t get_data() const {
394 static_copy_bytes<sizeof(bitfield_t) >()(gil_reinterpret_cast_c<const unsigned char*>(_data_ptr),gil_reinterpret_cast<unsigned char*>(&ret));
397 void set_data(const bitfield_t& val) const {
398 static_copy_bytes<sizeof(bitfield_t) >()(gil_reinterpret_cast_c<const unsigned char*>(&val),gil_reinterpret_cast<unsigned char*>(_data_ptr));
403 void set(integer_t value) const { // can this be done faster??
404 this->derived().set_unsafe(((value % num_values) + num_values) % num_values);
406 integer_t get() const { return derived().get(); }
407 const Derived& derived() const { return static_cast<const Derived&>(*this); }
409 } // namespace detail
411 /// \defgroup PackedChannelReferenceModel packed_channel_reference
412 /// \ingroup ChannelModel
413 /// \brief Represents a reference proxy to a channel operating over a bit range whose offset is fixed at compile time. Models ChannelConcept
416 /// // Reference to a 2-bit channel starting at bit 1 (i.e. the second bit)
417 /// using bits2_1_ref_t = packed_channel_reference<uint16_t,1,2,true> const;
420 /// bits2_1_ref_t channel_ref(&data);
421 /// channel_ref = channel_traits<bits2_1_ref_t>::max_value(); // == 3
422 /// assert(data == 6); // == 3<<1 == 6
425 /// \tparam BitField A type that holds the bits of the pixel from which the channel is referenced. Typically an integral type, like std::uint16_t
426 /// \tparam Defines the sequence of bits in the data value that contain the channel
427 /// \tparam true if the reference is mutable
428 template <typename BitField, int FirstBit, int NumBits, bool IsMutable>
429 class packed_channel_reference;
431 /// \tparam A type that holds the bits of the pixel from which the channel is referenced. Typically an integral type, like std::uint16_t
432 /// \tparam Defines the sequence of bits in the data value that contain the channel
433 /// \tparam true if the reference is mutable
434 template <typename BitField, int NumBits, bool IsMutable>
435 class packed_dynamic_channel_reference;
437 /// \ingroup PackedChannelReferenceModel
438 /// \brief A constant subbyte channel reference whose bit offset is fixed at compile time. Models ChannelConcept
439 template <typename BitField, int FirstBit, int NumBits>
440 class packed_channel_reference<BitField, FirstBit, NumBits, false>
441 : public detail::packed_channel_reference_base
443 packed_channel_reference<BitField, FirstBit, NumBits, false>,
449 using parent_t = detail::packed_channel_reference_base
451 packed_channel_reference<BitField, FirstBit, NumBits, false>,
457 friend class packed_channel_reference<BitField, FirstBit, NumBits, true>;
459 static const BitField channel_mask = static_cast<BitField>(parent_t::max_val) << FirstBit;
461 void operator=(packed_channel_reference const&);
463 using const_reference = packed_channel_reference<BitField,FirstBit,NumBits,false> const;
464 using mutable_reference = packed_channel_reference<BitField,FirstBit,NumBits,true> const;
465 using integer_t = typename parent_t::integer_t;
467 explicit packed_channel_reference(const void* data_ptr) : parent_t(data_ptr) {}
468 packed_channel_reference(const packed_channel_reference& ref) : parent_t(ref._data_ptr) {}
469 packed_channel_reference(const mutable_reference& ref) : parent_t(ref._data_ptr) {}
471 unsigned first_bit() const { return FirstBit; }
473 integer_t get() const { return integer_t((this->get_data()&channel_mask) >> FirstBit); }
476 /// \ingroup PackedChannelReferenceModel
477 /// \brief A mutable subbyte channel reference whose bit offset is fixed at compile time. Models ChannelConcept
478 template <typename BitField, int FirstBit, int NumBits>
479 class packed_channel_reference<BitField,FirstBit,NumBits,true>
480 : public detail::packed_channel_reference_base<packed_channel_reference<BitField,FirstBit,NumBits,true>,BitField,NumBits,true>
482 using parent_t = detail::packed_channel_reference_base<packed_channel_reference<BitField,FirstBit,NumBits,true>,BitField,NumBits,true>;
483 friend class packed_channel_reference<BitField,FirstBit,NumBits,false>;
485 static const BitField channel_mask = static_cast< BitField >( parent_t::max_val ) << FirstBit;
488 using const_reference = packed_channel_reference<BitField,FirstBit,NumBits,false> const;
489 using mutable_reference = packed_channel_reference<BitField,FirstBit,NumBits,true> const;
490 using integer_t = typename parent_t::integer_t;
492 explicit packed_channel_reference(void* data_ptr) : parent_t(data_ptr) {}
493 packed_channel_reference(const packed_channel_reference& ref) : parent_t(ref._data_ptr) {}
495 packed_channel_reference const& operator=(integer_t value) const
497 BOOST_ASSERT(value <= parent_t::max_val);
502 const packed_channel_reference& operator=(const mutable_reference& ref) const { set_from_reference(ref.get_data()); return *this; }
503 const packed_channel_reference& operator=(const const_reference& ref) const { set_from_reference(ref.get_data()); return *this; }
505 template <bool Mutable1>
506 const packed_channel_reference& operator=(const packed_dynamic_channel_reference<BitField,NumBits,Mutable1>& ref) const { set_unsafe(ref.get()); return *this; }
508 unsigned first_bit() const { return FirstBit; }
510 integer_t get() const { return integer_t((this->get_data()&channel_mask) >> FirstBit); }
511 void set_unsafe(integer_t value) const { this->set_data((this->get_data() & ~channel_mask) | (( static_cast< BitField >( value )<<FirstBit))); }
513 void set_from_reference(const BitField& other_bits) const { this->set_data((this->get_data() & ~channel_mask) | (other_bits & channel_mask)); }
516 }} // namespace boost::gil
519 // We are forced to define swap inside std namespace because on some platforms (Visual Studio 8) STL calls swap qualified.
520 // swap with 'left bias':
521 // - swap between proxy and anything
522 // - swap between value type and proxy
523 // - swap between proxy and proxy
525 /// \ingroup PackedChannelReferenceModel
526 /// \brief swap for packed_channel_reference
527 template <typename BF, int FB, int NB, bool M, typename R>
529 void swap(boost::gil::packed_channel_reference<BF, FB, NB, M> const x, R& y)
531 boost::gil::swap_proxy
533 typename boost::gil::packed_channel_reference<BF, FB, NB, M>::value_type
538 /// \ingroup PackedChannelReferenceModel
539 /// \brief swap for packed_channel_reference
540 template <typename BF, int FB, int NB, bool M>
543 typename boost::gil::packed_channel_reference<BF, FB, NB, M>::value_type& x,
544 boost::gil::packed_channel_reference<BF, FB, NB, M> const y)
546 boost::gil::swap_proxy
548 typename boost::gil::packed_channel_reference<BF, FB, NB, M>::value_type
552 /// \ingroup PackedChannelReferenceModel
553 /// \brief swap for packed_channel_reference
554 template <typename BF, int FB, int NB, bool M> inline
556 boost::gil::packed_channel_reference<BF, FB, NB, M> const x,
557 boost::gil::packed_channel_reference<BF, FB, NB, M> const y)
559 boost::gil::swap_proxy
561 typename boost::gil::packed_channel_reference<BF, FB, NB, M>::value_type
567 namespace boost { namespace gil {
569 /// \defgroup PackedChannelDynamicReferenceModel packed_dynamic_channel_reference
570 /// \ingroup ChannelModel
571 /// \brief Represents a reference proxy to a channel operating over a bit range whose offset is specified at run time. Models ChannelConcept
575 /// // Reference to a 2-bit channel whose offset is specified at construction time
576 /// using bits2_dynamic_ref_t = packed_dynamic_channel_reference<uint8_t,2,true> const;
579 /// bits2_dynamic_ref_t channel_ref(&data,1);
580 /// channel_ref = channel_traits<bits2_dynamic_ref_t>::max_value(); // == 3
581 /// assert(data == 6); // == (3<<1) == 6
584 /// \brief Models a constant subbyte channel reference whose bit offset is a runtime parameter. Models ChannelConcept
585 /// Same as packed_channel_reference, except that the offset is a runtime parameter
586 /// \ingroup PackedChannelDynamicReferenceModel
587 template <typename BitField, int NumBits>
588 class packed_dynamic_channel_reference<BitField,NumBits,false>
589 : public detail::packed_channel_reference_base<packed_dynamic_channel_reference<BitField,NumBits,false>,BitField,NumBits,false>
591 using parent_t = detail::packed_channel_reference_base<packed_dynamic_channel_reference<BitField,NumBits,false>,BitField,NumBits,false>;
592 friend class packed_dynamic_channel_reference<BitField,NumBits,true>;
594 unsigned _first_bit; // 0..7
596 void operator=(const packed_dynamic_channel_reference&);
598 using const_reference = packed_dynamic_channel_reference<BitField,NumBits,false> const;
599 using mutable_reference = packed_dynamic_channel_reference<BitField,NumBits,true> const;
600 using integer_t = typename parent_t::integer_t;
602 packed_dynamic_channel_reference(const void* data_ptr, unsigned first_bit) : parent_t(data_ptr), _first_bit(first_bit) {}
603 packed_dynamic_channel_reference(const const_reference& ref) : parent_t(ref._data_ptr), _first_bit(ref._first_bit) {}
604 packed_dynamic_channel_reference(const mutable_reference& ref) : parent_t(ref._data_ptr), _first_bit(ref._first_bit) {}
606 unsigned first_bit() const { return _first_bit; }
608 integer_t get() const {
609 const BitField channel_mask = static_cast< integer_t >( parent_t::max_val ) <<_first_bit;
610 return static_cast< integer_t >(( this->get_data()&channel_mask ) >> _first_bit );
614 /// \brief Models a mutable subbyte channel reference whose bit offset is a runtime parameter. Models ChannelConcept
615 /// Same as packed_channel_reference, except that the offset is a runtime parameter
616 /// \ingroup PackedChannelDynamicReferenceModel
617 template <typename BitField, int NumBits>
618 class packed_dynamic_channel_reference<BitField,NumBits,true>
619 : public detail::packed_channel_reference_base<packed_dynamic_channel_reference<BitField,NumBits,true>,BitField,NumBits,true>
621 using parent_t = detail::packed_channel_reference_base<packed_dynamic_channel_reference<BitField,NumBits,true>,BitField,NumBits,true>;
622 friend class packed_dynamic_channel_reference<BitField,NumBits,false>;
627 using const_reference = packed_dynamic_channel_reference<BitField,NumBits,false> const;
628 using mutable_reference = packed_dynamic_channel_reference<BitField,NumBits,true> const;
629 using integer_t = typename parent_t::integer_t;
631 packed_dynamic_channel_reference(void* data_ptr, unsigned first_bit) : parent_t(data_ptr), _first_bit(first_bit) {}
632 packed_dynamic_channel_reference(const packed_dynamic_channel_reference& ref) : parent_t(ref._data_ptr), _first_bit(ref._first_bit) {}
634 packed_dynamic_channel_reference const& operator=(integer_t value) const
636 BOOST_ASSERT(value <= parent_t::max_val);
641 const packed_dynamic_channel_reference& operator=(const mutable_reference& ref) const { set_unsafe(ref.get()); return *this; }
642 const packed_dynamic_channel_reference& operator=(const const_reference& ref) const { set_unsafe(ref.get()); return *this; }
644 template <typename BitField1, int FirstBit1, bool Mutable1>
645 const packed_dynamic_channel_reference& operator=(const packed_channel_reference<BitField1, FirstBit1, NumBits, Mutable1>& ref) const
646 { set_unsafe(ref.get()); return *this; }
648 unsigned first_bit() const { return _first_bit; }
650 integer_t get() const {
651 const BitField channel_mask = static_cast< integer_t >( parent_t::max_val ) << _first_bit;
652 return static_cast< integer_t >(( this->get_data()&channel_mask ) >> _first_bit );
655 void set_unsafe(integer_t value) const {
656 const BitField channel_mask = static_cast< integer_t >( parent_t::max_val ) << _first_bit;
657 this->set_data((this->get_data() & ~channel_mask) | value<<_first_bit);
660 } } // namespace boost::gil
663 // We are forced to define swap inside std namespace because on some platforms (Visual Studio 8) STL calls swap qualified.
664 // swap with 'left bias':
665 // - swap between proxy and anything
666 // - swap between value type and proxy
667 // - swap between proxy and proxy
670 /// \ingroup PackedChannelDynamicReferenceModel
671 /// \brief swap for packed_dynamic_channel_reference
672 template <typename BF, int NB, bool M, typename R> inline
673 void swap(const boost::gil::packed_dynamic_channel_reference<BF,NB,M> x, R& y) {
674 boost::gil::swap_proxy<typename boost::gil::packed_dynamic_channel_reference<BF,NB,M>::value_type>(x,y);
678 /// \ingroup PackedChannelDynamicReferenceModel
679 /// \brief swap for packed_dynamic_channel_reference
680 template <typename BF, int NB, bool M> inline
681 void swap(typename boost::gil::packed_dynamic_channel_reference<BF,NB,M>::value_type& x, const boost::gil::packed_dynamic_channel_reference<BF,NB,M> y) {
682 boost::gil::swap_proxy<typename boost::gil::packed_dynamic_channel_reference<BF,NB,M>::value_type>(x,y);
685 /// \ingroup PackedChannelDynamicReferenceModel
686 /// \brief swap for packed_dynamic_channel_reference
687 template <typename BF, int NB, bool M> inline
688 void swap(const boost::gil::packed_dynamic_channel_reference<BF,NB,M> x, const boost::gil::packed_dynamic_channel_reference<BF,NB,M> y) {
689 boost::gil::swap_proxy<typename boost::gil::packed_dynamic_channel_reference<BF,NB,M>::value_type>(x,y);
693 // \brief Determines the fundamental type which may be used, e.g., to cast from larger to smaller channel types.
694 namespace boost { namespace gil {
695 template <typename T>
696 struct base_channel_type_impl { using type = T; };
699 struct base_channel_type_impl<packed_channel_value<N> >
700 { using type = typename packed_channel_value<N>::integer_t; };
702 template <typename B, int F, int N, bool M>
703 struct base_channel_type_impl<packed_channel_reference<B, F, N, M> >
705 using type = typename packed_channel_reference<B,F,N,M>::integer_t;
708 template <typename B, int N, bool M>
709 struct base_channel_type_impl<packed_dynamic_channel_reference<B, N, M> >
711 using type = typename packed_dynamic_channel_reference<B,N,M>::integer_t;
714 template <typename ChannelValue, typename MinV, typename MaxV>
715 struct base_channel_type_impl<scoped_channel_value<ChannelValue, MinV, MaxV> >
716 { using type = ChannelValue; };
718 template <typename T>
719 struct base_channel_type : base_channel_type_impl<typename std::remove_cv<T>::type> {};
721 }} //namespace boost::gil