Re: [Boost-users] [GIL] Warnings when compiling items in channel_algorithms.hpp

Subject: Re: [Boost-users] [GIL] Warnings when compiling items in channel_algorithms.hpp
From: Nathan Crookston (nathan.crookston_at_[hidden])
Date: 2010-06-23 14:18:09

Hi Christian,

On Wed, Jun 23, 2010 at 10:42 AM, Christian Henning <chhenning_at_[hidden]> wrote:
>> The only difference between what you suggested and what I'm posting is
>> the addition of some explicit construction calls:
>
> I'm sorry I cannot make out your addition of some explicit constructor
> calls. Did you send the correct patch snippet? Could we just post the
> code without the patch syntax? I don't use patch.
>

Sorry, I could have been clearer.  The original code used only
explicit construction calls.  Your suggested code replaced them with
static_cast (which would work great if they were casting to the
correct type instead of just an integral type).  I found that both
were necessary to suppress warnings.  Here's the new code:

// 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 src_integer_t;
        typedef typename
unsigned_integral_max_value<DstChannelV>::value_type dst_integer_t;

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

} // namespace detail

/////////////////////////////////////////////////////
///  bits32f conversion
/////////////////////////////////////////////////////

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

Thanks for your help on this, and for you work on the library.  Good
luck on the IO review!

Nate