[css-color] Define 'linearRGB'

[dirkschulze]

SVG, CSS Masking and Filter Effects use linearRGB in some situations. See https://drafts.fxtf.org/filter-effects/#ColorInterpolationFiltersProperty
It would be great if we can combine the sRGB and linearRGB definition in one specification: CSS Colors. Furthermore, CSS Color currently supports the keyword srgb. It should also be considered to support sRGB for legacy reasons. (Ditto for linearrgb and linearRGB.)

As a consequence, the CSS properties in Filter Effects should support lowercase and camelcase versions of both keywords as well.

[svgeesus]

Yes, it makes sense to define this in Color 4.

[svgeesus]

CSS property values are not in general case-sensitive except as specially noted.

[dirkschulze]

Ah ok, I wonder if this breaks older SVG parsers w/o CSS support though. They might assume case sensitive attribute values for presentation attributes.

[tabatkins]

They very well might, but that's not really a concern - any new functionality addition at all will "break" an older implementation that doesn't understand the new functionality.

[svgeesus]

Spec now has linkable <dfn> for sRGB and for linear-light sRGB; the latter more verbose form chosen to resolve earlier comments that the term 'linear RGB' was underspecified.