Hi all,

ever since Jang Tongary suggested to use boost::fusion to define pixel
types I wondered what he meant by that.

I believe you're mentioning me here. ;-)

I never had the opportunity to
get myself familiar with fusion so I started learning it and I'm
really amazed how easy the library is to use. I think I'm at a point
where I would like to reach to the community for some advice.

The very idea is to use Fusion to manipulate the pixel, not defining the pixel, though you could do it.

I have one file "adapted_pixel.hpp" that adapts GIL pixel (concept) to Fusion Associative Sequence. Though I want to share here but there's another dependency on my other header.

Let's say I wanna create a homogeneous three channel pixel type, like
RGB. For that I would use a fusion map since I want to access channel
by name. I also would like to be able to swap channels around to
create BGR. How would I do that?

namespace boost { namespace gil_3 {

struct red_t;
struct green_t;
struct blue_t;

} } // namespace boost::gil_3

void foo()
{
typedef fusion::map< fusion::pair< gil_3::red_t , boost::uint8_t >
, fusion::pair< gil_3::green_t, boost::uint8_t >
, fusion::pair< gil_3::blue_t , boost::uint8_t >
> rgb8_pixel_t;

// not working
typedef fusion::reverse_view< rgb8_pixel_t >::type bgr8_pixel_t;

rgb8_pixel_t a( 10, 20, 30 );
bgr8_pixel_t b( 30, 20, 10 );

boost::uint8_t red_a = fusion::at_key< gil_3::red_t >( a );
boost::uint8_t red_b = fusion::at_key< gil_3::red_t >( b );
}

reverse_view is a view after all, so you can't instantiate it with ( 30, 20, 10 ).

If you wanna define the reverse one, then fusion::map<..in reverse order...>.

I'm happy with the way that GIL defines the pixel, what Fusion really shines here is the generalized way to manipulate the data.

HTH