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Re: luminanceToAlpha values in FEColorMatrix

From: Chris Lilley <chris@w3.org>
Date: Mon, 5 Sep 2011 22:59:37 +0200
Message-ID: <2110558260.20110905225937@w3.org>
To: Rik Cabanier <cabanier@gmail.com>
CC: David Woolley <forums@david-woolley.me.uk>, Dean Jackson <dino@apple.com>, <public-fx@w3.org>, www-svg <www-svg@w3.org>
On Sunday, September 4, 2011, 6:06:01 AM, Rik wrote:

RC> I agree.I don't know what makes sRGB so special that it is the
RC> default colorspace in SVG and used all over the spec.

Because it was proposed (and accepted) as a standard default space, in the days when colour management was something that applied solely to high-end printing and Apple was trying to bring it to the desktop while other platforms were silent on the subject or in ostrich mode.

So HTML 3.2 and 4 use it, and CSS 1 and 2. Thus, SVG did also.

RC> Shouldn't SVG be color space agnostic (like PDF and Postscript)?

Agnostic can easily translate to 'throw any value as at the screen and hope for the best'. That wasn't really good enough in 1980 and is certainly not good enough, even as a lowest common denominator, now. Consumer electronics has settled on sRGB while desktops and laptops (but not mobile, yet) has settled on ICC v.4 as a base capability.

So sRGB as a default was a reasonable choice in 1996 and remains (arguably, has wider industry support) as a fallback for less capable devices in 2011.

So I would disagree on 'agnostic'[1] as a goal, but if you rephrase to "shouldn't SVG allow other colour spaces as well" then I would be in full agreement. As long as there is a clear fallback.

RC>  There are several parts in the spec that talk about 'linear RGB' vs sRGB that are very confusing.

Could you explain why it is confusing. The equations (in both directions) are given, and are fairly simple.

RC> Maybe there is some history here that I'm not aware of...

Quite a bit, yes.


[1] Either from Ancient Greek ???????? (agn?stos, ?ignorant, not knowing?) or from a- + Gnostic. Deriving (either way) from Ancient Greek ?- (a-, ?not?) + ???????? (gign?sk?, ?I know?).

-- 
 Chris Lilley   Technical Director, Interaction Domain                 
 W3C Graphics Activity Lead, Fonts Activity Lead
 Co-Chair, W3C Hypertext CG
 Member, CSS, WebFonts, SVG Working Groups
Received on Monday, 5 September 2011 21:00:13 GMT

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