Re: [Boost-users] [GIL] Why does 'get_color' take a tag object instead of its type only?

Subject: Re: [Boost-users] [GIL] Why does 'get_color' take a tag object instead of its type only?
From: TONGARI (tongari95_at_[hidden])
Date: 2013-01-29 10:59:20

2013/1/29 Christian Henning <chhenning_at_[hidden]>

> By tag is useful when dealing with swapped channels, like rgb and bgr.
> For instance when reading a bmp file I read it as bgr but the end user
> most likely wants the rgb format.
>

Uh... maybe I didn't express clearly.
It's currently defined as:

    template <typename ColorBase, typename Color>
    get_color(ColorBase& cb, Color=Color())

I just want to know why not just take Color by the type, e.g.

    template <typename Color, typename ColorBase>
    get_color(ColorBase& cb)

> I'm not sure I follow your arguments. Why would you care for the tag?
> Just take the number of channels and enumerate over them. Is that not
> general enough for you?
>
> But maybe you wanna specialize your algorithm by the pixel layout
> type, e.g. rgb_layout_t.
>
> >
> >>
> >> >
> >> > And if possible, I hope GIL would just make pixel a Fusion sequence.
> >> >
> >>
> >> I'm very interested in ideas to improve gil! Since I'm not familiar
> >> with a fusion sequence could you elaborate a little further.
> >
> >
> > I imagine it to be an Associative Sequence in Fusion (naturally or
> adapted).
> > So I can just use the algorithms provided by Fusion, which seem to
> overwhelm
> > the static_xxxs in GIL.
>
> Can it handle swapped channels? Like:
>
> rgb8_pixel_t a( 10, 20, 30 );
> bgr8_pixel_t b( 30, 20, 10 );
>
> assert( get_color( a, red_t() ) == get_color( b, red_t() ) );
>

I'm trying the non-intrusive (adapted) approach to make it a Fusion
Sequence, I'll back to here when done.

Code above could be rewritten as:
fusion::at_key<red_t>(a) == fusion::at_key<red_t>(b)