Re: [filter-effects] hue-rotate() and saturate() filters

On Tue, Oct 15, 2013 at 2:37 AM, Dirk Schulze <dschulze@adobe.com> wrote:
> On Oct 14, 2013, at 11:28 AM, Chris Lilley <chris@w3.org> wrote:
> Shouldn't the conversion between RGB and HSL be bijective? So if both color spaces are bijective, the algorithm described by feColorMatrix must be wrong[1]. Polar coordinates or not, every color in HSL should be describable in RGB. And we still do the animation on the hue value and not on the RGB values. It also depends of course if the definition of hue in Filter Effects is equivalent to the definition of hue in HSL. Same (and probably more dramatic) for saturate. SVG 1.1 is not very clear about that.

Yes, the RGB<->HSL conversion is bijective, but that doesn't
intrinsically have anything to do with <feColorMatrix>, as it's not
trying to do anything in HSL space.

The definition of "hue" is indeed the same between HSL and what
<feColorMatrix huerotate> is doing (it's the same in *every*
hue-angle-using colorspace I've ever heard of), but it's got a
different definition of saturation and lightness.

~TJ

Received on Tuesday, 15 October 2013 15:41:48 UTC