Re: [boost] GIL Review

From: Fernando Cacciola (fernando_cacciola_at_[hidden])
Date: 2006-11-01 08:54:36

Joel de Guzman wrote:
> Fernando Cacciola wrote:
> 
>>Joel de Guzman wrote:
>>
>>>Joel de Guzman wrote:
>>>
>>>
>>>>Matt Gruenke wrote:
>>>>
>>>>
>>>>>Joel de Guzman wrote:
>>>>>
>>>>>>I disagree. A color space is a tuple of numbers. It is concerned with
>>>>>>data and layout as far as I can see. That is the very definition of
>>>>>>"tuple".
>>>>>>
>>>>>
>>>>>That's a color (or pixel value).
>>>>>
>>>>>A color space provides the semantics of these numbers, possibly 
>>>>>including how they are converted to other color spaces.  This may 
>>>>>include its basis, CIE primaries, transfer function, gamut, etc.  (For 
>>>>>more information, here's a good starting point: 
>>>>>http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html )
>>>>>
>>>>>A pixel format establishes the mapping between channels of an image 
>>>>>(i.e. color, pixel value, etc.) and components of a color space.
>>>>
>>>>Now I see the confusion. There are overlaps in the definition of
>>>>colors and color-spaces of course. Did you think they were orthogonal?
>>>>See: http://tinyurl.com/18r for the definition of color-spaces.
>>>
>>>tinyurl mistake again! One more try:
>>>
>>>     http://tinyurl.com/veebq
>>>
>>>Regards,
>>
>>That very same wikipedia article may be used to explain why Matt and I 
>>are against using the term "color space" for the GIL element under 
>>discussion.
>>If you read it carefully you can see that the "tuple of numbers" is a 
>>"color model", not a "color space" (a mapping function binds the model 
>>with the space)
>>Reading further down you see that it refers to "RGB", "CYMK", etc as 
>>color models, not color spaces.
>>
>>So at most I would say that the correct term is color model. It 
>>certainly isn't color space and that article shows why quite well.
> 
> 
> No! 
 >
What no exactly?

 > Color space is gamut (footprint) + color model.

Right, and this is in contradiction with? (from what I wrote)

Anyway, as you know by now my problem was the tag. I wouldn't mind 
speaking of color spaces in the context of the pixel<> class (which 
plays the role of a color<> class).
Although in that case I would add a side note in the docs explaining 
that instances of the class represents "points" in the color space 
rather than the color space itself as a whole (something which could be 
represented by a class, but isn't in the case of GIL)

Fernando Cacciola