ChannelR operator()(typename channel_traits<Channel1>::const_reference ch1, typename channel_traits<Channel2>::const_reference ch2) const { return ChannelR(ch1)/ChannelR(ch2); }
ChannelR operator()(typename channel_traits<Channel>::const_reference ch, const Scalar& s) const { return ChannelR(ch-s); }
GIL_FORCEINLINE ChannelR operator( )( typename channel_traits<Channel>::const_reference ch ) const { return std::sqrt( ChannelR( ch ) ); }