- From: Brian Manthos <brianman@microsoft.com>
- Date: Sat, 30 Jul 2011 02:43:15 +0000
- To: Alan Gresley <alan@css-class.com>, Tab Atkins Jr. <jackalmage@gmail.com>
- CC: Leif Arne Storset <lstorset@opera.com>, Brad Kemper <brad.kemper@gmail.com>, "www-style@w3.org" <www-style@w3.org>
Alan Gresley: (a) > background: white -o-linear-gradient(left, red, transparent, blue); (b) > background: white -o-linear-gradient(left, red, rgba(255,0,0,0) 50%, > rgba(0,0,255,0) 50%, blue); > > Then how is it possible that Opera renders both these gradients the > same? One has one midpoint color stop and the other has two midpoint > color stops. It's fairly straightforward, IMO, given that Opera seems to be applying pre-multiplied color interpolation. non-premultiplied a0 red, transparent, blue a1 red 0%, transparent 50%, blue 100% a2 red 0%, rgba(0,0,0,0) 50%, blue 100% premultiplied a3 red 0%, prgba(0,0,0,0) 50%, blue 100% non-premultiplied b0 red, rgba(255,0,0,0) 50%, rgba(0,0,255,0) 50%, blue b1 red 0%, rgba(255,0,0,0) 50%, rgba(0,0,255,0) 50%, blue 100% premultiplied b1 red 0%, prgba(0,0,0,0) 50%, prgba(0,0,0,0) 50%, blue 100% All 7 render the same, but behave differently when transitions and animations are involved (3 stops for a0/a1/a2/a3 vs. 4 stops for b0/b1/b2). In case it's useful, try changing transparent to rgba(0,0,0,0) in (a) and you'll notice the rendering is unchanged in browsers that use pre-multiplied color interpolation. Another approach that might prove useful to evaluate is to use opacities of 0.5 instead of 0.
Received on Saturday, 30 July 2011 02:43:45 UTC