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

Hello Tab,

Tuesday, October 15, 2013, 5:41:00 PM, you wrote:

> 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

In fact, no. feColormatrix is simply an affine 3D transformation of an
RGB cube while HSL involves conversion to a hexagonal shape and then
projection of that:

"The hue is the proportion of the distance around the edge of the
hexagon which passes through the projected point,"
http://en.wikipedia.org/wiki/HSL_and_HSV#Hue_and_chroma




-- 
Best regards,
 Chris                            mailto:chris@w3.org

Received on Tuesday, 15 October 2013 16:11:25 UTC