Re: [svgwg] 'color-interpolation' isn't used for alpha compositing (#366)

> If they had read the specification, they would have instantly realized that three items of information they requested are in fact clearly stated, and need not be "assumed".

I was stricly reacting to the term (as I wrote), but I read the current specification, and the writing is sloppy. Call me pedantic but quoting some parts:

> The color-interpolation property chooses between color operations occurring in the sRGB color space or in a (light energy linear) linearized RGB color space.

*or in a (light energy linear) linearized RGB color space*

Which one? 

*light energy linear*, the proper terminology is **radiometrically linear**, you will probably not find *light energy linear* in color science literature.

It is only toward the bottom that you finally find what is hiding under **Linear RGB**:

> The conversion formulas between the sRGB color space (i.e., nonlinear with 2.2 gamma curve) and the linearized RGB color space (i.e., color values expressed as sRGB tristimulus values without a gamma curve) can be found in the sRGB specification [SRGB].

It is a shame that the 1999 specification was better authored in that regard and was unambiguous:

> RGB colors are specified in the sRGB color space [9]. UAs may vary in the fidelity with which they represent these colors, but use of sRGB provides an unambiguous and objectively measurable definition of what the color should be, which can be related to international standards [10].

This should have been the very first paragraph, but back in 1999, sRGB specification was only 3 years old. There is no reason to not have it clearly stated at the very start of the current specification.

> there was no "assumption" of the sRGB primaries, D50 whitepoint, and sRGB or linear transfer function (as appropriate);

_D50_, are you certain? ;)

All in all, the [CSS 4 draft](https://drafts.csswg.org/css-color-4/#predefined) is much better written in that regard and you will notice that it indeed specify the three components so that no ambiguity is possible.


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Received on Thursday, 7 February 2019 19:30:03 UTC