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

Hello Michael,

Sunday, October 13, 2013, 5:53:20 AM, you wrote:

Thanks for carefully demonstrating the problem with examples.

> I do understand that because these filters are a linear matrix
> approximation and remain in RGB space, there will be inaccuracies
> when trying to do HSL ops,

Your analysis is correct as to the reason

>  but these seem very extreme to me, and
> very unexpected. But they seem to be consistent between Firefox and
> Webkit/Blink - (when converted to SVG equivalents) - so I do not think this is a bug.

Yes, this is not a bug (the implementations are following the
specification), from SVG1

> Has there been any thought of converting content to HSL before
> applying these filter shorthands? Or adding true HSL primitives to
> the filter toolbox? (Something like an feFuncH or feFuncS). 

Also correct that changing the colourspace used for computations to
one using polar coordinates would give more intuitive results.

SVG has a color-interpolation property which is used for
non-filter operations; in SVG2 this is updated to add two polar spaces
(HSL and CIELCHab). The same addition could be made to
color-interpolation-filters.

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