jf barraud wrote:
... I suspect we are using premultiplied alpha where normal colors should be used, but I remember I already bumped into similar strongly non intuitive conventions of svg with this respect (maybe the same one, I don't remember), so I'm not sure.
No, it's not a premultiplied/non-premultiplied issue (btw, in the standard, if it doesn't say it's non-premultiplied it is premultiplied, it says so in section 15.7.1 of SVG 1.1). Rather, it has to do with Inkscape's lack of support for the color-interpolation-filters attribute (in combination with the extremely unintuitive decision to give color-interpolation-filters a different initial value than color-interpolation).
In SVG there are two attributes that determine the color space used for operating on color values, these are color-interpolation and color-interpolation-filters (both can be set to either linearRGB or sRGB). For some reason that is completely beyond me the W3C decided to make the initial value sRGB for color-interpolation and linearRGB for color-interpolation-filters... As Inkscape has no support whatsoever for color-interpolation-filters pretty much any file which uses a filter looks wrong in Inkscape.
To ensure that your file looks the same in Inkscape as in other viewers, use color-interpolation-filters="sRGB" (as far as I know it's perfectly valid to do this just once, on the root SVG element). I've attached a file that shows how Batik renders filters-turb-01-f.svg with this modification.
