channel_algorithm.hpp

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/*
    Copyright 2005-2007 Adobe Systems Incorporated
   
    Use, modification and distribution are subject to the Boost Software License,
    Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
    http://www.boost.org/LICENSE_1_0.txt).

    See http://opensource.adobe.com/gil for most recent version including documentation.
*/
/*************************************************************************************************/

#ifndef GIL_CHANNEL_ALGORITHM_HPP
#define GIL_CHANNEL_ALGORITHM_HPP


#include "gil_config.hpp"
#include "channel.hpp"
#include <boost/mpl/less.hpp>
#include <boost/mpl/integral_c.hpp>
#include <boost/mpl/greater.hpp>
#include <boost/type_traits.hpp>

namespace boost { namespace gil {

//#ifdef _MSC_VER
//#pragma warning(push)
//#pragma warning(disable: 4309)      // disable truncation of constant value warning (using -1 to get the max value of an integral)
//#endif

namespace detail {

// some forward declarations
template <typename SrcChannelV, typename DstChannelV, bool SrcIsIntegral, bool DstIsIntegral> struct channel_converter_unsigned_impl;
template <typename SrcChannelV, typename DstChannelV, bool SrcIsGreater> struct channel_converter_unsigned_integral;
template <typename SrcChannelV, typename DstChannelV, bool SrcLessThanDst, bool SrcDivisible> struct channel_converter_unsigned_integral_impl;
template <typename SrcChannelV, typename DstChannelV, bool SrcLessThanDst, bool CannotFitInInteger> struct channel_converter_unsigned_integral_nondivisible;



template <typename UnsignedIntegralChannel>
struct unsigned_integral_max_value : public mpl::integral_c<UnsignedIntegralChannel,-1> {};

template <>
struct unsigned_integral_max_value<uint8_t> : public mpl::integral_c<uint32_t,0xFF> {};
template <>
struct unsigned_integral_max_value<uint16_t> : public mpl::integral_c<uint32_t,0xFFFF> {};
template <>
struct unsigned_integral_max_value<uint32_t> : public mpl::integral_c<uintmax_t,0xFFFFFFFF> {};


template <int K>
struct unsigned_integral_max_value<packed_channel_value<K> >
    : public mpl::integral_c<typename packed_channel_value<K>::integer_t, (1<<K)-1> {};


template <typename UnsignedIntegralChannel>
struct unsigned_integral_num_bits : public mpl::int_<sizeof(UnsignedIntegralChannel)*8> {};

template <int K>
struct unsigned_integral_num_bits<packed_channel_value<K> >
    : public mpl::int_<K> {};

} // namespace detail





template <typename SrcChannelV, typename DstChannelV>     // Model ChannelValueConcept
struct channel_converter_unsigned
    : public detail::channel_converter_unsigned_impl<SrcChannelV,DstChannelV,is_integral<SrcChannelV>::value,is_integral<DstChannelV>::value> {};


template <typename T> struct channel_converter_unsigned<T,T> : public detail::identity<T> {};


namespace detail {


template <typename SrcChannelV, typename DstChannelV, bool SrcIsIntegral, bool DstIsIntegral> 
struct channel_converter_unsigned_impl : public std::unary_function<DstChannelV,SrcChannelV> {
    DstChannelV operator()(SrcChannelV src) const { 
        return DstChannelV(channel_traits<DstChannelV>::min_value() +
            (src - channel_traits<SrcChannelV>::min_value()) / channel_range<SrcChannelV>() * channel_range<DstChannelV>()); 
    }
private:
    template <typename C>
    static double channel_range() {
        return double(channel_traits<C>::max_value()) - double(channel_traits<C>::min_value());
    }
};

// When both the source and the destination are integral channels, perform a faster conversion
template <typename SrcChannelV, typename DstChannelV> 
struct channel_converter_unsigned_impl<SrcChannelV,DstChannelV,true,true>
    : public channel_converter_unsigned_integral<SrcChannelV,DstChannelV,
    mpl::less<unsigned_integral_max_value<SrcChannelV>,unsigned_integral_max_value<DstChannelV> >::value > {};



template <typename SrcChannelV, typename DstChannelV> 
struct channel_converter_unsigned_integral<SrcChannelV,DstChannelV,true>
    : public channel_converter_unsigned_integral_impl<SrcChannelV,DstChannelV,true,
    !(unsigned_integral_max_value<DstChannelV>::value % unsigned_integral_max_value<SrcChannelV>::value) > {};

template <typename SrcChannelV, typename DstChannelV> 
struct channel_converter_unsigned_integral<SrcChannelV,DstChannelV,false>
    : public channel_converter_unsigned_integral_impl<SrcChannelV,DstChannelV,false,
    !(unsigned_integral_max_value<SrcChannelV>::value % unsigned_integral_max_value<DstChannelV>::value) > {};



// Both source and destination are unsigned integral channels, 
// the src max value is less than the dst max value,
// and the dst max value is divisible by the src max value
template <typename SrcChannelV, typename DstChannelV> 
struct channel_converter_unsigned_integral_impl<SrcChannelV,DstChannelV,true,true> {
    DstChannelV operator()(SrcChannelV src) const { 
        typedef typename unsigned_integral_max_value<DstChannelV>::value_type integer_t;
        static const integer_t mul = unsigned_integral_max_value<DstChannelV>::value / unsigned_integral_max_value<SrcChannelV>::value;
        return DstChannelV(src * mul);
    }
};

// Both source and destination are unsigned integral channels, 
// the dst max value is less than (or equal to) the src max value,
// and the src max value is divisible by the dst max value
template <typename SrcChannelV, typename DstChannelV> 
struct channel_converter_unsigned_integral_impl<SrcChannelV,DstChannelV,false,true> {
    DstChannelV operator()(SrcChannelV src) const { 
        typedef typename unsigned_integral_max_value<SrcChannelV>::value_type integer_t;
        static const integer_t div = unsigned_integral_max_value<SrcChannelV>::value / unsigned_integral_max_value<DstChannelV>::value;
        static const integer_t div2 = div/2;
        return DstChannelV((src + div2) / div);
    }
};

// Prevent overflow for the largest integral type
template <typename DstChannelV> 
struct channel_converter_unsigned_integral_impl<uintmax_t,DstChannelV,false,true> {
    DstChannelV operator()(uintmax_t src) const { 
        static const uintmax_t div = unsigned_integral_max_value<bits32>::value / unsigned_integral_max_value<DstChannelV>::value;
        static const uintmax_t div2 = div/2;
        if (src > unsigned_integral_max_value<uintmax_t>::value - div2)
            return unsigned_integral_max_value<DstChannelV>::value;
        return DstChannelV((src + div2) / div);
    }
};

// Both source and destination are unsigned integral channels, 
// and the dst max value is not divisible by the src max value
// See if you can represent the expression (src * dst_max) / src_max in integral form
template <typename SrcChannelV, typename DstChannelV, bool SrcLessThanDst> 
struct channel_converter_unsigned_integral_impl<SrcChannelV,DstChannelV,SrcLessThanDst,false> 
    : public channel_converter_unsigned_integral_nondivisible<SrcChannelV,DstChannelV,SrcLessThanDst,
    mpl::greater<
        mpl::plus<unsigned_integral_num_bits<SrcChannelV>,unsigned_integral_num_bits<DstChannelV> >,
        unsigned_integral_num_bits<uintmax_t>
    >::value> {};


// Both source and destination are unsigned integral channels, 
// the src max value is less than the dst max value,
// and the dst max value is not divisible by the src max value
// The expression (src * dst_max) / src_max fits in an integer
template <typename SrcChannelV, typename DstChannelV> 
struct channel_converter_unsigned_integral_nondivisible<SrcChannelV,DstChannelV,true,false> {
    DstChannelV operator()(SrcChannelV src) const {
        typedef typename detail::min_fast_uint<unsigned_integral_num_bits<SrcChannelV>::value+unsigned_integral_num_bits<DstChannelV>::value>::type integer_t;
        return DstChannelV(integer_t(src * unsigned_integral_max_value<DstChannelV>::value) / unsigned_integral_max_value<SrcChannelV>::value);
    }
};

// Both source and destination are unsigned integral channels, 
// the src max value is less than the dst max value,
// and the dst max value is not divisible by the src max value
// The expression (src * dst_max) / src_max cannot fit in an integer (overflows). Use a double
template <typename SrcChannelV, typename DstChannelV> 
struct channel_converter_unsigned_integral_nondivisible<SrcChannelV,DstChannelV,true,true> {
    DstChannelV operator()(SrcChannelV src) const {
        static const double mul = unsigned_integral_max_value<DstChannelV>::value / double(unsigned_integral_max_value<SrcChannelV>::value);
        return DstChannelV(src * mul);
    }
};


// Both source and destination are unsigned integral channels, 
// the dst max value is less than (or equal to) the src max value,
// and the src max value is not divisible by the dst max value
template <typename SrcChannelV, typename DstChannelV, bool CannotFit> 
struct channel_converter_unsigned_integral_nondivisible<SrcChannelV,DstChannelV,false,CannotFit> {
    DstChannelV operator()(SrcChannelV src) const { 
        typedef typename unsigned_integral_max_value<SrcChannelV>::value_type integer_t;

        static const double div = unsigned_integral_max_value<SrcChannelV>::value / double(unsigned_integral_max_value<DstChannelV>::value);
        static const integer_t div2 = integer_t(div/2);
        return DstChannelV((src + div2) / div);
    }
};

} // namespace detail


template <typename DstChannelV> struct channel_converter_unsigned<bits32f,DstChannelV> : public std::unary_function<bits32f,DstChannelV> {
    DstChannelV   operator()(bits32f x) const { return DstChannelV(x*channel_traits<DstChannelV>::max_value()+0.5f); }
};

template <typename SrcChannelV> struct channel_converter_unsigned<SrcChannelV,bits32f> : public std::unary_function<SrcChannelV,bits32f> {
    bits32f operator()(SrcChannelV   x) const { return bits32f(x/float(channel_traits<SrcChannelV>::max_value())); }
};

template <> struct channel_converter_unsigned<bits32f,bits32f> : public std::unary_function<bits32f,bits32f> {
    bits32f operator()(bits32f   x) const { return x; }
};


template <> struct channel_converter_unsigned<bits32,bits32f> : public std::unary_function<bits32,bits32f> {
    bits32f operator()(bits32 x) const { 
        // 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
        if (x>=channel_traits<bits32>::max_value()) return channel_traits<bits32f>::max_value();
        return float(x) / float(channel_traits<bits32>::max_value());
    }
};
template <> struct channel_converter_unsigned<bits32f,bits32> : public std::unary_function<bits32f,bits32> {
    bits32 operator()(bits32f x) const { 
        // 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
        if (x>=channel_traits<bits32f>::max_value()) return channel_traits<bits32>::max_value();
        return bits32(x * channel_traits<bits32>::max_value() + 0.5f); 
    }
};


namespace detail {
// Converting from signed to unsigned integral channel. 
// It is both a unary function, and a metafunction (thus requires the 'type' nested typedef, which equals result_type)
template <typename ChannelValue>     // Model ChannelValueConcept
struct channel_convert_to_unsigned : public detail::identity<ChannelValue> {
    typedef ChannelValue type;
};

template <> struct channel_convert_to_unsigned<bits8s> : public std::unary_function<bits8s,bits8> { 
    typedef bits8 type;
    type operator()(bits8s  val) const { return val+128; } 
};

template <> struct channel_convert_to_unsigned<bits16s> : public std::unary_function<bits16s,bits16> { 
    typedef bits16 type;
    type operator()(bits16s  val) const { return val+32768; } 
};

template <> struct channel_convert_to_unsigned<bits32s> : public std::unary_function<bits32s,bits32> {
    typedef bits32 type;
    type operator()(bits32s x) const { return static_cast<bits32>(x+(1<<31)); }
};


// Converting from unsigned to signed integral channel
// It is both a unary function, and a metafunction (thus requires the 'type' nested typedef, which equals result_type)
template <typename ChannelValue>     // Model ChannelValueConcept
struct channel_convert_from_unsigned : public detail::identity<ChannelValue> {
    typedef ChannelValue type;
};

template <> struct channel_convert_from_unsigned<bits8s> : public std::unary_function<bits8,bits8s> { 
    typedef bits8s type;
    type  operator()(bits8  val) const { return val-128; } 
};

template <> struct channel_convert_from_unsigned<bits16s> : public std::unary_function<bits16,bits16s> { 
    typedef bits16s type;
    type operator()(bits16 val) const { return val-32768; } 
};

template <> struct channel_convert_from_unsigned<bits32s> : public std::unary_function<bits32,bits32s> {
    typedef bits32s type;
    type operator()(bits32 x) const { return static_cast<bits32s>(x-(1<<31)); }
};

}   // namespace detail

template <typename SrcChannelV, typename DstChannelV> // Model ChannelValueConcept
struct channel_converter : public std::unary_function<SrcChannelV,DstChannelV> {
    DstChannelV operator()(SrcChannelV src) const {
        typedef detail::channel_convert_to_unsigned<SrcChannelV> to_unsigned;
        typedef detail::channel_convert_from_unsigned<DstChannelV>   from_unsigned;
        typedef channel_converter_unsigned<typename to_unsigned::result_type, typename from_unsigned::argument_type> converter_unsigned;
        return from_unsigned()(converter_unsigned()(to_unsigned()(src))); 
    }
};

template <typename DstChannel, typename SrcChannel> // Model ChannelConcept (could be channel references)
inline typename channel_traits<DstChannel>::value_type channel_convert(SrcChannel src) { 
    return channel_converter<typename channel_traits<SrcChannel>::value_type,
                             typename channel_traits<DstChannel>::value_type>()(src); 
}

struct default_channel_converter {
    template <typename Ch1, typename Ch2>
    void operator()(const Ch1& src, Ch2& dst) const {
        dst=channel_convert<Ch2>(src);
    }
};

namespace detail {
    // fast integer division by 255
    inline uint32_t div255(uint32_t in) { uint32_t tmp=in+128; return (tmp + (tmp>>8))>>8; }

    // fast integer divison by 32768
    inline uint32_t div32768(uint32_t in) { return (in+16384)>>15; }
}



template <typename ChannelValue>
struct channel_multiplier_unsigned : public std::binary_function<ChannelValue,ChannelValue,ChannelValue> {
    ChannelValue operator()(ChannelValue a, ChannelValue b) const {
        return ChannelValue(a / double(channel_traits<ChannelValue>::max_value()) * b);
    }
};

template<> struct channel_multiplier_unsigned<bits8> : public std::binary_function<bits8,bits8,bits8> {
    bits8 operator()(bits8 a, bits8 b) const { return bits8(detail::div255(uint32_t(a) * uint32_t(b))); }
};

template<> struct channel_multiplier_unsigned<bits16> : public std::binary_function<bits16,bits16,bits16> {
    bits16 operator()(bits16 a, bits16 b) const { return bits16((uint32_t(a) * uint32_t(b))/65535); }
};

template<> struct channel_multiplier_unsigned<bits32f> : public std::binary_function<bits32f,bits32f,bits32f> {
    bits32f operator()(bits32f a, bits32f b) const { return a*b; }
};

template <typename ChannelValue>
struct channel_multiplier : public std::binary_function<ChannelValue, ChannelValue, ChannelValue> {
    ChannelValue operator()(ChannelValue a, ChannelValue b) const {
        typedef detail::channel_convert_to_unsigned<ChannelValue> to_unsigned;
        typedef detail::channel_convert_from_unsigned<ChannelValue>   from_unsigned;
        typedef channel_multiplier_unsigned<typename to_unsigned::result_type> multiplier_unsigned;
        return from_unsigned()(multiplier_unsigned()(to_unsigned()(a), to_unsigned()(b))); 
    }
};

template <typename Channel> // Models ChannelConcept (could be a channel reference)
inline typename channel_traits<Channel>::value_type channel_multiply(Channel a, Channel b) { 
    return channel_multiplier<typename channel_traits<Channel>::value_type>()(a,b);
}



template <typename Channel> // Models ChannelConcept (could be a channel reference)
inline typename channel_traits<Channel>::value_type channel_invert(Channel x) { 
    return channel_traits<Channel>::max_value()-x + channel_traits<Channel>::min_value(); 
}

//#ifdef _MSC_VER
//#pragma warning(pop)
//#endif

} }  // namespace boost::gil

#endif