[whatwg] several messages
ian at hixie.ch
Wed May 16 16:25:31 PDT 2007
On Fri, 21 Jul 2006, Henri Sivonen wrote:
> I gather that a normative reference to the PorterDuff paper is needed:
On Mon, 24 Jul 2006, L. David Baron wrote:
> I've written tests for the 11 operators defined in the paper, plus a
> test for 'darker' that assumes Quartz's PlusDarker operator :
> It seems like 'darker' is currently not interoperable, and might be
> unlikely to become interoperable, due to different availability of
> compositing operators across platforms. (Quartz has PlusDarker. Mozilla
> uses the saturate operator that is provided by Cairo/libpixman (and also
> by XRender), which is described in  and , but seems to me to be
> quite different.)
> One solution to that problem would be to remove 'darker' from the spec
> rather than defining it one way or the other. Thoughts?
I've referenced the paper and dropped 'darker'.
On Wed, 28 Mar 2007, Philip Taylor wrote:
> [snip a very long and detailed discussion of the operators, with much
Wow. Thanks! Based on David's input above and on your own advice, and on
Vlad's later comments, I've simply removed 'darker' and referenced
Porter-Duff for the others.
On Wed, 4 Apr 2007, Vladimir Vukicevic wrote:
> Well, if we have lighter, we should keep darker; I think that for
> mozilla at least, we can implement this using some slow-boat fallback
> mechanism -- basically, render the path/image to a separate surface,
> then manually do the requested math if things don't map directly to one
> of our operators; this is what our SVG impl does now for many of the SVG
According to David, 'lighter' is just Porter-Duff's 'plus'. Is that not
right? For now I've left it, with that definition.
Ian Hickson U+1047E )\._.,--....,'``. fL
http://ln.hixie.ch/ U+263A /, _.. \ _\ ;`._ ,.
Things that are impossible just take longer. `._.-(,_..'--(,_..'`-.;.'
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