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 00:52:24

2013/1/28 Christian Henning <chhenning_at_[hidden]>

> Hi,
>
> On Mon, Jan 28, 2013 at 9:53 AM, TONGARI <tongari95_at_[hidden]> wrote:
> > Hi there,
> >
> > I'm curious of why gil::get_color(pixel, tag) is defined that way.
> > Any need to take the tag value?
> >
> > If not, I'd prefer gil::get_color<Tag>(pixel) or just
> gil::get<Tag>(pixel)
> > or even Tag::get(pixel).
>
> You can use the "at_c" function.
>
> rgb8_pixel_t p( 10, 20, 30);
> unsigned char c = at_c<0>( p );
> assert( c == 10 );
>

That doesn't really answer my question...
I just wonder the rationale for taking the tag value.

I know there are at_c/semantic_at_c things, but they don't fit my need.
Those functions are useful if I'm an end-user who knows the exact format,
but I'm writing a 2D graphics lib building on GIL that intends to support
all types the user gave,
so index means nothing here, I must get the component by tag, thus
get<red_t>(c) won't compile if the user gives cmyk.

> >
> > 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.

Thanks.