1 | /* |
2 | Copyright 2005-2007 Adobe Systems Incorporated |
3 | |
4 | Use, modification and distribution are subject to the Boost Software License, |
5 | Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
6 | http://www.boost.org/LICENSE_1_0.txt). |
7 | |
8 | See http://opensource.adobe.com/gil for most recent version including documentation. |
9 | */ |
10 | /*************************************************************************************************/ |
11 | |
12 | #ifndef GIL_CHANNEL_ALGORITHM_HPP |
13 | #define GIL_CHANNEL_ALGORITHM_HPP |
14 | |
15 | //////////////////////////////////////////////////////////////////////////////////////// |
16 | /// \file |
17 | /// \brief Channel algorithms |
18 | /// \author Lubomir Bourdev and Hailin Jin \n |
19 | /// Adobe Systems Incorporated |
20 | /// \date 2005-2007 \n Last updated on May 6, 2007 |
21 | /// |
22 | /// Definitions of standard GIL 8-bit, 16-bit, 32-bit channels |
23 | /// |
24 | //////////////////////////////////////////////////////////////////////////////////////// |
25 | |
26 | #include "gil_config.hpp" |
27 | #include "channel.hpp" |
28 | #include <boost/mpl/less.hpp> |
29 | #include <boost/mpl/integral_c.hpp> |
30 | #include <boost/mpl/greater.hpp> |
31 | #include <boost/type_traits.hpp> |
32 | |
33 | namespace boost { namespace gil { |
34 | |
35 | //#ifdef _MSC_VER |
36 | //#pragma warning(push) |
37 | //#pragma warning(disable: 4309) // disable truncation of constant value warning (using -1 to get the max value of an integral) |
38 | //#endif |
39 | |
40 | namespace detail { |
41 | |
42 | // some forward declarations |
43 | template <typename SrcChannelV, typename DstChannelV, bool SrcIsIntegral, bool DstIsIntegral> struct channel_converter_unsigned_impl; |
44 | template <typename SrcChannelV, typename DstChannelV, bool SrcIsGreater> struct channel_converter_unsigned_integral; |
45 | template <typename SrcChannelV, typename DstChannelV, bool SrcLessThanDst, bool SrcDivisible> struct channel_converter_unsigned_integral_impl; |
46 | template <typename SrcChannelV, typename DstChannelV, bool SrcLessThanDst, bool CannotFitInInteger> struct channel_converter_unsigned_integral_nondivisible; |
47 | |
48 | ////////////////////////////////////// |
49 | //// unsigned_integral_max_value - given an unsigned integral channel type, returns its maximum value as an MPL integral constant |
50 | ////////////////////////////////////// |
51 | |
52 | |
53 | template <typename UnsignedIntegralChannel> |
54 | struct unsigned_integral_max_value : public mpl::integral_c<UnsignedIntegralChannel,-1> {}; |
55 | |
56 | template <> |
57 | struct unsigned_integral_max_value<uint8_t> : public mpl::integral_c<uint32_t,0xFF> {}; |
58 | template <> |
59 | struct unsigned_integral_max_value<uint16_t> : public mpl::integral_c<uint32_t,0xFFFF> {}; |
60 | template <> |
61 | struct unsigned_integral_max_value<uint32_t> : public mpl::integral_c<uintmax_t,0xFFFFFFFF> {}; |
62 | |
63 | |
64 | template <int K> |
65 | struct unsigned_integral_max_value<packed_channel_value<K> > |
66 | : public mpl::integral_c<typename packed_channel_value<K>::integer_t, (1<<K)-1> {}; |
67 | |
68 | ////////////////////////////////////// |
69 | //// unsigned_integral_num_bits - given an unsigned integral channel type, returns the minimum number of bits needed to represent it |
70 | ////////////////////////////////////// |
71 | |
72 | template <typename UnsignedIntegralChannel> |
73 | struct unsigned_integral_num_bits : public mpl::int_<sizeof(UnsignedIntegralChannel)*8> {}; |
74 | |
75 | template <int K> |
76 | struct unsigned_integral_num_bits<packed_channel_value<K> > |
77 | : public mpl::int_<K> {}; |
78 | |
79 | } // namespace detail |
80 | |
81 | /** |
82 | \defgroup ChannelConvertAlgorithm channel_convert |
83 | \brief Converting from one channel type to another |
84 | \ingroup ChannelAlgorithm |
85 | |
86 | Conversion is done as a simple linear mapping of one channel range to the other, |
87 | such that the minimum/maximum value of the source maps to the minimum/maximum value of the destination. |
88 | One implication of this is that the value 0 of signed channels may not be preserved! |
89 | |
90 | When creating new channel models, it is often a good idea to provide specializations for the channel conversion algorithms, for |
91 | example, for performance optimizations. If the new model is an integral type that can be signed, it is easier to define the conversion |
92 | only for the unsigned type (\p channel_converter_unsigned) and provide specializations of \p detail::channel_convert_to_unsigned |
93 | and \p detail::channel_convert_from_unsigned to convert between the signed and unsigned type. |
94 | |
95 | Example: |
96 | \code |
97 | // bits32f is a floating point channel with range [0.0f ... 1.0f] |
98 | bits32f src_channel = channel_traits<bits32f>::max_value(); |
99 | assert(src_channel == 1); |
100 | |
101 | // bits8 is 8-bit unsigned integral channel (typedef-ed from unsigned char) |
102 | bits8 dst_channel = channel_convert<bits8>(src_channel); |
103 | assert(dst_channel == 255); // max value goes to max value |
104 | \endcode |
105 | */ |
106 | |
107 | /** |
108 | \defgroup ChannelConvertUnsignedAlgorithm channel_converter_unsigned |
109 | \ingroup ChannelConvertAlgorithm |
110 | \brief Convert one unsigned/floating point channel to another. Converts both the channel type and range |
111 | @{ |
112 | */ |
113 | |
114 | ////////////////////////////////////// |
115 | //// channel_converter_unsigned |
116 | ////////////////////////////////////// |
117 | |
118 | template <typename SrcChannelV, typename DstChannelV> // Model ChannelValueConcept |
119 | struct channel_converter_unsigned |
120 | : public detail::channel_converter_unsigned_impl<SrcChannelV,DstChannelV,is_integral<SrcChannelV>::value,is_integral<DstChannelV>::value> {}; |
121 | |
122 | |
123 | /// \brief Converting a channel to itself - identity operation |
124 | template <typename T> struct channel_converter_unsigned<T,T> : public detail::identity<T> {}; |
125 | |
126 | |
127 | namespace detail { |
128 | |
129 | ////////////////////////////////////// |
130 | //// channel_converter_unsigned_impl |
131 | ////////////////////////////////////// |
132 | |
133 | /// \brief This is the default implementation. Performance specializatons are provided |
134 | template <typename SrcChannelV, typename DstChannelV, bool SrcIsIntegral, bool DstIsIntegral> |
135 | struct channel_converter_unsigned_impl : public std::unary_function<DstChannelV,SrcChannelV> { |
136 | DstChannelV operator()(SrcChannelV src) const { |
137 | return DstChannelV(channel_traits<DstChannelV>::min_value() + |
138 | (src - channel_traits<SrcChannelV>::min_value()) / channel_range<SrcChannelV>() * channel_range<DstChannelV>()); |
139 | } |
140 | private: |
141 | template <typename C> |
142 | static double channel_range() { |
143 | return double(channel_traits<C>::max_value()) - double(channel_traits<C>::min_value()); |
144 | } |
145 | }; |
146 | |
147 | // When both the source and the destination are integral channels, perform a faster conversion |
148 | template <typename SrcChannelV, typename DstChannelV> |
149 | struct channel_converter_unsigned_impl<SrcChannelV,DstChannelV,true,true> |
150 | : public channel_converter_unsigned_integral<SrcChannelV,DstChannelV, |
151 | mpl::less<unsigned_integral_max_value<SrcChannelV>,unsigned_integral_max_value<DstChannelV> >::value > {}; |
152 | |
153 | |
154 | ////////////////////////////////////// |
155 | //// channel_converter_unsigned_integral |
156 | ////////////////////////////////////// |
157 | |
158 | template <typename SrcChannelV, typename DstChannelV> |
159 | struct channel_converter_unsigned_integral<SrcChannelV,DstChannelV,true> |
160 | : public channel_converter_unsigned_integral_impl<SrcChannelV,DstChannelV,true, |
161 | !(unsigned_integral_max_value<DstChannelV>::value % unsigned_integral_max_value<SrcChannelV>::value) > {}; |
162 | |
163 | template <typename SrcChannelV, typename DstChannelV> |
164 | struct channel_converter_unsigned_integral<SrcChannelV,DstChannelV,false> |
165 | : public channel_converter_unsigned_integral_impl<SrcChannelV,DstChannelV,false, |
166 | !(unsigned_integral_max_value<SrcChannelV>::value % unsigned_integral_max_value<DstChannelV>::value) > {}; |
167 | |
168 | |
169 | ////////////////////////////////////// |
170 | //// channel_converter_unsigned_integral_impl |
171 | ////////////////////////////////////// |
172 | |
173 | // Both source and destination are unsigned integral channels, |
174 | // the src max value is less than the dst max value, |
175 | // and the dst max value is divisible by the src max value |
176 | template <typename SrcChannelV, typename DstChannelV> |
177 | struct channel_converter_unsigned_integral_impl<SrcChannelV,DstChannelV,true,true> { |
178 | DstChannelV operator()(SrcChannelV src) const { |
179 | typedef typename unsigned_integral_max_value<DstChannelV>::value_type integer_t; |
180 | static const integer_t mul = unsigned_integral_max_value<DstChannelV>::value / unsigned_integral_max_value<SrcChannelV>::value; |
181 | return DstChannelV(src * mul); |
182 | } |
183 | }; |
184 | |
185 | // Both source and destination are unsigned integral channels, |
186 | // the dst max value is less than (or equal to) the src max value, |
187 | // and the src max value is divisible by the dst max value |
188 | template <typename SrcChannelV, typename DstChannelV> |
189 | struct channel_converter_unsigned_integral_impl<SrcChannelV,DstChannelV,false,true> { |
190 | DstChannelV operator()(SrcChannelV src) const { |
191 | typedef typename unsigned_integral_max_value<SrcChannelV>::value_type integer_t; |
192 | static const integer_t div = unsigned_integral_max_value<SrcChannelV>::value / unsigned_integral_max_value<DstChannelV>::value; |
193 | static const integer_t div2 = div/2; |
194 | return DstChannelV((src + div2) / div); |
195 | } |
196 | }; |
197 | |
198 | // Prevent overflow for the largest integral type |
199 | template <typename DstChannelV> |
200 | struct channel_converter_unsigned_integral_impl<uintmax_t,DstChannelV,false,true> { |
201 | DstChannelV operator()(uintmax_t src) const { |
202 | static const uintmax_t div = unsigned_integral_max_value<bits32>::value / unsigned_integral_max_value<DstChannelV>::value; |
203 | static const uintmax_t div2 = div/2; |
204 | if (src > unsigned_integral_max_value<uintmax_t>::value - div2) |
205 | return unsigned_integral_max_value<DstChannelV>::value; |
206 | return DstChannelV((src + div2) / div); |
207 | } |
208 | }; |
209 | |
210 | // Both source and destination are unsigned integral channels, |
211 | // and the dst max value is not divisible by the src max value |
212 | // See if you can represent the expression (src * dst_max) / src_max in integral form |
213 | template <typename SrcChannelV, typename DstChannelV, bool SrcLessThanDst> |
214 | struct channel_converter_unsigned_integral_impl<SrcChannelV,DstChannelV,SrcLessThanDst,false> |
215 | : public channel_converter_unsigned_integral_nondivisible<SrcChannelV,DstChannelV,SrcLessThanDst, |
216 | mpl::greater< |
217 | mpl::plus<unsigned_integral_num_bits<SrcChannelV>,unsigned_integral_num_bits<DstChannelV> >, |
218 | unsigned_integral_num_bits<uintmax_t> |
219 | >::value> {}; |
220 | |
221 | |
222 | // Both source and destination are unsigned integral channels, |
223 | // the src max value is less than the dst max value, |
224 | // and the dst max value is not divisible by the src max value |
225 | // The expression (src * dst_max) / src_max fits in an integer |
226 | template <typename SrcChannelV, typename DstChannelV> |
227 | struct channel_converter_unsigned_integral_nondivisible<SrcChannelV,DstChannelV,true,false> { |
228 | DstChannelV operator()(SrcChannelV src) const { |
229 | typedef typename detail::min_fast_uint<unsigned_integral_num_bits<SrcChannelV>::value+unsigned_integral_num_bits<DstChannelV>::value>::type integer_t; |
230 | return DstChannelV(integer_t(src * unsigned_integral_max_value<DstChannelV>::value) / unsigned_integral_max_value<SrcChannelV>::value); |
231 | } |
232 | }; |
233 | |
234 | // Both source and destination are unsigned integral channels, |
235 | // the src max value is less than the dst max value, |
236 | // and the dst max value is not divisible by the src max value |
237 | // The expression (src * dst_max) / src_max cannot fit in an integer (overflows). Use a double |
238 | template <typename SrcChannelV, typename DstChannelV> |
239 | struct channel_converter_unsigned_integral_nondivisible<SrcChannelV,DstChannelV,true,true> { |
240 | DstChannelV operator()(SrcChannelV src) const { |
241 | static const double mul = unsigned_integral_max_value<DstChannelV>::value / double(unsigned_integral_max_value<SrcChannelV>::value); |
242 | return DstChannelV(src * mul); |
243 | } |
244 | }; |
245 | |
246 | // Both source and destination are unsigned integral channels, |
247 | // the dst max value is less than (or equal to) the src max value, |
248 | // and the src max value is not divisible by the dst max value |
249 | template <typename SrcChannelV, typename DstChannelV, bool CannotFit> |
250 | struct channel_converter_unsigned_integral_nondivisible<SrcChannelV,DstChannelV,false,CannotFit> { |
251 | DstChannelV operator()(SrcChannelV src) const { |
252 | |
253 | typedef typename detail::unsigned_integral_max_value< SrcChannelV >::value_type src_integer_t; |
254 | typedef typename detail::unsigned_integral_max_value< DstChannelV >::value_type dst_integer_t; |
255 | |
256 | static const double div = unsigned_integral_max_value<SrcChannelV>::value |
257 | / static_cast< double >( unsigned_integral_max_value<DstChannelV>::value ); |
258 | |
259 | static const src_integer_t div2 = static_cast< src_integer_t >( div / 2.0 ); |
260 | |
261 | return DstChannelV( static_cast< dst_integer_t >(( static_cast< double >( src + div2 ) / div ))); |
262 | } |
263 | }; |
264 | |
265 | } // namespace detail |
266 | |
267 | ///////////////////////////////////////////////////// |
268 | /// bits32f conversion |
269 | ///////////////////////////////////////////////////// |
270 | |
271 | template <typename DstChannelV> struct channel_converter_unsigned<bits32f,DstChannelV> : public std::unary_function<bits32f,DstChannelV> { |
272 | DstChannelV operator()(bits32f x) const |
273 | { |
274 | typedef typename detail::unsigned_integral_max_value< DstChannelV >::value_type dst_integer_t; |
275 | return DstChannelV( static_cast< dst_integer_t >(x*channel_traits<DstChannelV>::max_value()+0.5f )); |
276 | } |
277 | }; |
278 | |
279 | template <typename SrcChannelV> struct channel_converter_unsigned<SrcChannelV,bits32f> : public std::unary_function<SrcChannelV,bits32f> { |
280 | bits32f operator()(SrcChannelV x) const { return bits32f(x/float(channel_traits<SrcChannelV>::max_value())); } |
281 | }; |
282 | |
283 | template <> struct channel_converter_unsigned<bits32f,bits32f> : public std::unary_function<bits32f,bits32f> { |
284 | bits32f operator()(bits32f x) const { return x; } |
285 | }; |
286 | |
287 | |
288 | /// \brief 32 bit <-> float channel conversion |
289 | template <> struct channel_converter_unsigned<bits32,bits32f> : public std::unary_function<bits32,bits32f> { |
290 | bits32f operator()(bits32 x) const { |
291 | // unfortunately without an explicit check it is possible to get a round-off error. We must ensure that max_value of bits32 matches max_value of bits32f |
292 | if (x>=channel_traits<bits32>::max_value()) return channel_traits<bits32f>::max_value(); |
293 | return float(x) / float(channel_traits<bits32>::max_value()); |
294 | } |
295 | }; |
296 | /// \brief 32 bit <-> float channel conversion |
297 | template <> struct channel_converter_unsigned<bits32f,bits32> : public std::unary_function<bits32f,bits32> { |
298 | bits32 operator()(bits32f x) const { |
299 | // unfortunately without an explicit check it is possible to get a round-off error. We must ensure that max_value of bits32 matches max_value of bits32f |
300 | if (x>=channel_traits<bits32f>::max_value()) return channel_traits<bits32>::max_value(); |
301 | return bits32(x * channel_traits<bits32>::max_value() + 0.5f); |
302 | } |
303 | }; |
304 | |
305 | /// @} |
306 | |
307 | namespace detail { |
308 | // Converting from signed to unsigned integral channel. |
309 | // It is both a unary function, and a metafunction (thus requires the 'type' nested typedef, which equals result_type) |
310 | template <typename ChannelValue> // Model ChannelValueConcept |
311 | struct channel_convert_to_unsigned : public detail::identity<ChannelValue> { |
312 | typedef ChannelValue type; |
313 | }; |
314 | |
315 | template <> struct channel_convert_to_unsigned<bits8s> : public std::unary_function<bits8s,bits8> { |
316 | typedef bits8 type; |
317 | type operator()(bits8s val) const { return val+128; } |
318 | }; |
319 | |
320 | template <> struct channel_convert_to_unsigned<bits16s> : public std::unary_function<bits16s,bits16> { |
321 | typedef bits16 type; |
322 | type operator()(bits16s val) const { return val+32768; } |
323 | }; |
324 | |
325 | template <> struct channel_convert_to_unsigned<bits32s> : public std::unary_function<bits32s,bits32> { |
326 | typedef bits32 type; |
327 | type operator()(bits32s x) const { return static_cast<bits32>(x+(1<<31)); } |
328 | }; |
329 | |
330 | |
331 | // Converting from unsigned to signed integral channel |
332 | // It is both a unary function, and a metafunction (thus requires the 'type' nested typedef, which equals result_type) |
333 | template <typename ChannelValue> // Model ChannelValueConcept |
334 | struct channel_convert_from_unsigned : public detail::identity<ChannelValue> { |
335 | typedef ChannelValue type; |
336 | }; |
337 | |
338 | template <> struct channel_convert_from_unsigned<bits8s> : public std::unary_function<bits8,bits8s> { |
339 | typedef bits8s type; |
340 | type operator()(bits8 val) const { return val-128; } |
341 | }; |
342 | |
343 | template <> struct channel_convert_from_unsigned<bits16s> : public std::unary_function<bits16,bits16s> { |
344 | typedef bits16s type; |
345 | type operator()(bits16 val) const { return val-32768; } |
346 | }; |
347 | |
348 | template <> struct channel_convert_from_unsigned<bits32s> : public std::unary_function<bits32,bits32s> { |
349 | typedef bits32s type; |
350 | type operator()(bits32 x) const { return static_cast<bits32s>(x-(1<<31)); } |
351 | }; |
352 | |
353 | } // namespace detail |
354 | |
355 | /// \ingroup ChannelConvertAlgorithm |
356 | /// \brief A unary function object converting between channel types |
357 | template <typename SrcChannelV, typename DstChannelV> // Model ChannelValueConcept |
358 | struct channel_converter : public std::unary_function<SrcChannelV,DstChannelV> { |
359 | DstChannelV operator()(const SrcChannelV& src) const { |
360 | typedef detail::channel_convert_to_unsigned<SrcChannelV> to_unsigned; |
361 | typedef detail::channel_convert_from_unsigned<DstChannelV> from_unsigned; |
362 | typedef channel_converter_unsigned<typename to_unsigned::result_type, typename from_unsigned::argument_type> converter_unsigned; |
363 | return from_unsigned()(converter_unsigned()(to_unsigned()(src))); |
364 | } |
365 | }; |
366 | |
367 | /// \ingroup ChannelConvertAlgorithm |
368 | /// \brief Converting from one channel type to another. |
369 | template <typename DstChannel, typename SrcChannel> // Model ChannelConcept (could be channel references) |
370 | inline typename channel_traits<DstChannel>::value_type channel_convert(const SrcChannel& src) { |
371 | return channel_converter<typename channel_traits<SrcChannel>::value_type, |
372 | typename channel_traits<DstChannel>::value_type>()(src); |
373 | } |
374 | |
375 | /// \ingroup ChannelConvertAlgorithm |
376 | /// \brief Same as channel_converter, except it takes the destination channel by reference, which allows |
377 | /// us to move the templates from the class level to the method level. This is important when invoking it |
378 | /// on heterogeneous pixels. |
379 | struct default_channel_converter { |
380 | template <typename Ch1, typename Ch2> |
381 | void operator()(const Ch1& src, Ch2& dst) const { |
382 | dst=channel_convert<Ch2>(src); |
383 | } |
384 | }; |
385 | |
386 | namespace detail { |
387 | // fast integer division by 255 |
388 | inline uint32_t div255(uint32_t in) { uint32_t tmp=in+128; return (tmp + (tmp>>8))>>8; } |
389 | |
390 | // fast integer divison by 32768 |
391 | inline uint32_t div32768(uint32_t in) { return (in+16384)>>15; } |
392 | } |
393 | |
394 | /** |
395 | \defgroup ChannelMultiplyAlgorithm channel_multiply |
396 | \ingroup ChannelAlgorithm |
397 | \brief Multiplying unsigned channel values of the same type. Performs scaled multiplication result = a * b / max_value |
398 | |
399 | Example: |
400 | \code |
401 | bits8 x=128; |
402 | bits8 y=128; |
403 | bits8 mul = channel_multiply(x,y); |
404 | assert(mul == 64); // 64 = 128 * 128 / 255 |
405 | \endcode |
406 | */ |
407 | /// @{ |
408 | |
409 | /// \brief This is the default implementation. Performance specializatons are provided |
410 | template <typename ChannelValue> |
411 | struct channel_multiplier_unsigned : public std::binary_function<ChannelValue,ChannelValue,ChannelValue> { |
412 | ChannelValue operator()(ChannelValue a, ChannelValue b) const { |
413 | return ChannelValue(a / double(channel_traits<ChannelValue>::max_value()) * b); |
414 | } |
415 | }; |
416 | |
417 | /// \brief Specialization of channel_multiply for 8-bit unsigned channels |
418 | template<> struct channel_multiplier_unsigned<bits8> : public std::binary_function<bits8,bits8,bits8> { |
419 | bits8 operator()(bits8 a, bits8 b) const { return bits8(detail::div255(in: uint32_t(a) * uint32_t(b))); } |
420 | }; |
421 | |
422 | /// \brief Specialization of channel_multiply for 16-bit unsigned channels |
423 | template<> struct channel_multiplier_unsigned<bits16> : public std::binary_function<bits16,bits16,bits16> { |
424 | bits16 operator()(bits16 a, bits16 b) const { return bits16((uint32_t(a) * uint32_t(b))/65535); } |
425 | }; |
426 | |
427 | /// \brief Specialization of channel_multiply for float 0..1 channels |
428 | template<> struct channel_multiplier_unsigned<bits32f> : public std::binary_function<bits32f,bits32f,bits32f> { |
429 | bits32f operator()(bits32f a, bits32f b) const { return a*b; } |
430 | }; |
431 | |
432 | /// \brief A function object to multiply two channels. result = a * b / max_value |
433 | template <typename ChannelValue> |
434 | struct channel_multiplier : public std::binary_function<ChannelValue, ChannelValue, ChannelValue> { |
435 | ChannelValue operator()(ChannelValue a, ChannelValue b) const { |
436 | typedef detail::channel_convert_to_unsigned<ChannelValue> to_unsigned; |
437 | typedef detail::channel_convert_from_unsigned<ChannelValue> from_unsigned; |
438 | typedef channel_multiplier_unsigned<typename to_unsigned::result_type> multiplier_unsigned; |
439 | return from_unsigned()(multiplier_unsigned()(to_unsigned()(a), to_unsigned()(b))); |
440 | } |
441 | }; |
442 | |
443 | /// \brief A function multiplying two channels. result = a * b / max_value |
444 | template <typename Channel> // Models ChannelConcept (could be a channel reference) |
445 | inline typename channel_traits<Channel>::value_type channel_multiply(Channel a, Channel b) { |
446 | return channel_multiplier<typename channel_traits<Channel>::value_type>()(a,b); |
447 | } |
448 | /// @} |
449 | |
450 | /** |
451 | \defgroup ChannelInvertAlgorithm channel_invert |
452 | \ingroup ChannelAlgorithm |
453 | \brief Returns the inverse of a channel. result = max_value - x + min_value |
454 | |
455 | Example: |
456 | \code |
457 | // bits8 == uint8_t == unsigned char |
458 | bits8 x=255; |
459 | bits8 inv = channel_invert(x); |
460 | assert(inv == 0); |
461 | \endcode |
462 | */ |
463 | |
464 | /// \brief Default implementation. Provide overloads for performance |
465 | /// \ingroup ChannelInvertAlgorithm channel_invert |
466 | template <typename Channel> // Models ChannelConcept (could be a channel reference) |
467 | inline typename channel_traits<Channel>::value_type channel_invert(Channel x) { |
468 | return channel_traits<Channel>::max_value()-x + channel_traits<Channel>::min_value(); |
469 | } |
470 | |
471 | //#ifdef _MSC_VER |
472 | //#pragma warning(pop) |
473 | //#endif |
474 | |
475 | } } // namespace boost::gil |
476 | |
477 | #endif |
478 | |