- From: Osmo Jaakkola <orbik@iki.fi>
- Date: Wed, 09 Feb 2011 18:51:16 +0200
- To: www-svg@w3.org
> All white rects have the same transparency level and are drawn onto a > solid black background. Just the rects on the first row are filled with > either #7F7F7F or #BBBBBB but don't test color-interpolationat all. >> Yes. On both the source and the background. > Ok, this is maybe the point where I have the understanding problems. I > still read the Spec this way: At first we have the canvas, where > everything is drawn on by the compositing algorithm mentioned on thelink > you posted. > Now we want to draw a shape onto this canvas in the color spacelinearRGB > while the canvas itself is in sRGB. >For a better understanding I'll take a surface/buffer where I draw the > shape onto. This surface with the shape gets transformed to linearRGB. > Now I draw this surface on the canvas by compositing it with the > algorithm of the spec respecting the transparence that is set by the > property 'fill-opacity'. >For the example on the test suite, it means we would draw the rect onto > the canvas with the fill color white. Now we transform this surface to > linearRGB. But because we filled the shape with white: rgb(255,255,255) > the linearRGB transformation doesn't influence the surface. According to > the sRGB to linearRGB algorithm of the Spec, the resulting color values > are rgb(255,255,255). > At the end we draw the surface on the canvas with the 'fill-opcity:0.5' > by compositing it to the canvas. >The background is black, so we see the same gray independent if we draw > the rect with linearRGB or sRGB. > We might of course see a difference if we'd use another fill color than > white. But I don't get it why we should see a difference on this test. Because the alpha blending is done in linear RGB, and needs to be converted back to the parent's (canvas') color space. Background = sRGB(0, 0, 0) => linRGB(0, 0, 0) Foreground = sRGB(1.0, 1.0, 1.0) => linRGB(1.0, 1.0, 1.0) Opacity = 0.5 Result = linRGB(0.5, 0.5, 0.5) => sRGB(0.735, 0.735, 0.735)
Received on Wednesday, 9 February 2011 19:34:37 UTC