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Re: painting-render-02-b.svg

From: Chris Lilley <chris@w3.org>
Date: Fri, 22 Oct 2010 20:56:16 +0200
Message-ID: <1885682859.20101022205616@w3.org>
To: Dirk Schulze <vbs85@gmx.de>
CC: www-svg@w3.org
On Friday, October 22, 2010, 1:33:53 PM, Dirk wrote:

DS> Hi folks,

DS> I was looking at painting-render-02-b.html recently and I am a bit confused.
DS> The tests should test the correct handling of
DS> color-interpolation. Different rects have different properties of
DS> color-interpolation: auto, sRGB, linearRGB and inherit.
DS> But my understanding was that color-interpolation (or
DS> transforming sRGB colors to linearRGB colors and back) just
DS> influence the channels red, green and blue.

Yes. On both the source and the background.

DS> The rects on the test, with the different color-interpolations,
DS> are filled with the color 'white'. According to the algorithm on
DS> [1], the color spaces linearRGB and sRGB provide the same color
DS> values. Both results are 255,255,255, independent if you transform
DS> sRGB to linearRGB or back. So why should we see a difference between the rects?

See 14.2 Simple alpha compositing
http://www.w3.org/TR/SVG/masking.html#SimpleAlphaBlending

the white, semiopaque rects are being composited onto rectangles filled with either  #7F7F7F or #BBBBBB and the result will differ depending on the color-interpolation value.


-- 
 Chris Lilley   Technical Director, Interaction Domain                 
 W3C Graphics Activity Lead, Fonts Activity Lead
 Co-Chair, W3C Hypertext CG
 Member, CSS, WebFonts, SVG Working Groups
Received on Sunday, 24 October 2010 14:18:29 GMT

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