[Webkit-unassigned] [Bug 72411] filter that does nothing still does something

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=72411





--- Comment #6 from Dirk Schulze <krit at webkit.org>  2011-11-16 23:05:13 PST ---
(In reply to comment #5)
> (In reply to comment #4)
> > (In reply to comment #3)
> > > So the bug is probably "Why isn't SVG filters using the same color profile as the rest of the page?"
> > 
> > The default color space for SVG Filters is 'linearRGB'. The color space can be set with the CSS property 'color-interpolation-filters'. At the moment 'linearRGB' is the only color space that we support for SVG Filters. Please see also:
> > 
> > http://dev.w3.org/Graphics-FX/modules/filters/publish/SVGFilter.html#FilterPrimitivesOverviewIntro
> > http://www.w3.org/TR/2003/REC-SVG11-20030114/painting.html#ColorInterpolationFiltersProperty
> 
> I guess I misunderstood that property to mean that it applies to the filter operations themselves, not to the rendering of the output into the document.
> 
> I think this is an issue because it means there currently is no way to provide a filter that doesn't change its input, unless your system is set to linearRGB (or sRGB when we support it).

The default color space of SVG Masking was changed from linearRGB to sRGB as default (can be changed with 'color-interpolation' property). Maybe the same could be done for filters with changing the initial value of 'color-interpolation-filters'? This needs to get discussed on public-fx, since HTML doesn't support linearRGB yet IIRC. Maybe linearRGB could be added beside the supported color spaces sRGB and DeviceRGB. It is already an option in ColorSpace.h, just the CSS parser doesn't support it yet.

Supporting sRGB for filters is not a big deal. When I implemented linearRGB, I had problems to understand if the input of an effect needs to get transformed to linearRGB/sRGB or if the result needs to get transformed (the CSS property gets applied to certain effects). What happens if an effect has two inputs, both in different color spaces? I wrote some tests and couldn't get a sense full explanation of the behavior on testing other SVG Viewers.
At the end I decided to use linearRGB as default and support 'color-interpolation-filters' later. We already have a bug report for this: bug 6033. And I think this bug is a duplication of bug 6033 .

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