Re: [boost] [GIL] kth_channel_view

Subject: Re: [boost] [GIL] kth_channel_view
From: fabien.castan_at_[hidden]
Date: 2010-06-24 08:31:01

>A good example of using kth_channel_view is this:
>
>    rgb8_image_t img( 100, 100 );
>    typedef typename kth_channel_view_type< 0, const rgb8_view_t>::type view_t;
>    view_t first = kth_channel_view<0>( const_view( img ));

Another interesting possibility is:
    typedef kth_channel_view_type< 0, const rgb8_view_t> KthChannelView;
    typename KthChannelView::type first = KthChannelView::make( const_view(img) );

It can be a good thing to directly use channel type, like this:
    typedef channel_view_type< red_t, const rgb8_view_t>::type view_t;
    view_t first = channel_view<red_t>( const_view( img ));

I have written some code to do that, based on kth_channel_view_type. It's maybe intersting to include in gil.

Regards,
Fabien

namespace boost {
namespace gil {

template <typename Channel, typename View>
struct channel_type_to_index
{
        static const int value = gil::detail::type_to_index<
                                      typename color_space_type<View>::type, // color (mpl::vector)
                                                          Channel // channel type
		                    >::type::value; //< index of the channel in the color (mpl::vector)
};

template <typename Channel, typename View>
struct channel_view_type : public kth_channel_view_type<channel_type_to_index<Channel,View>::value, View>
{
        static const int index = channel_type_to_index<Channel,View>::value;
        typedef kth_channel_view_type<index, View> parent_t;
    typedef typename parent_t::type type;
    static type make(const View& src) { return parent_t::make(src); }
};

/// \ingroup ImageViewTransformationsKthChannel
template <typename Channel, typename View>
typename channel_view_type<Channel,View>::type channel_view(const View& src)
{
    return channel_view_type<Channel,View>::make(src);
}

}}