[whatwg] [canvas] inner shadows
dschulze at adobe.com
Fri Nov 23 15:49:53 PST 2012
On Nov 23, 2012, at 2:36 PM, Ian Hickson <ian at hixie.ch> wrote:
> On Fri, 21 Sep 2012, Tyler Larson wrote:
>> On Sep 20, 2012, at 6:49 PM, Ian Hickson <ian at hixie.ch> wrote:
>>> Can't you do this using clip() easily enough? Maybe I'm missing
>>> something important here. Can you elaborate?
>> Here is an example of what I am talking about.
>> Clip would mask something but adding an inner shadow is different and
>> pretty difficult to reproduce when you take into account complex shapes.
> Ah, yeah, I see what you mean. The problem is that the canvas rendering
> model always renders the shadow under the shape, and uses the shape's
> alpha to work out where to paint the shape.
> What we could do is offer control that would change the shadows from
> rendering under the shape to rendering over the shape, or, maybe even
> better, have a mode that only renders the shadows. Then you could achieve
> these effects relatively easily (by clipping to the shape so that the
> shadow only renders inside the shape).
Dependent if Canvas supports Filter Effects in the future or not (including SVG filters), the overlay shadow can be done with a combination of SourceAlpha and gaussian blur. There are already Canvas libraries that offer SVG Filters on Canvas.
> Is this something implementors would be interested in?
> Ian Hickson U+1047E )\._.,--....,'``. fL
> http://ln.hixie.ch/ U+263A /, _.. \ _\ ;`._ ,.
> Things that are impossible just take longer. `._.-(,_..'--(,_..'`-.;.'
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