[whatwg] Canvas Proposal: aliasClipping property

Ian Hickson ian at hixie.ch
Thu Oct 15 18:37:17 PDT 2009

On Sat, 3 Oct 2009, Charles Pritchard wrote:
> In some implementations: when drawImage is used along with a clipping 
> path, feathering is applied. This shows up in several projective 
> transformation demos contrasting Firefox with Chrome.
> [...]

On Sun, 4 Oct 2009, Marius Gundersen wrote:
> [...] it could perhaps include all the other drawing options, like 
> stroking and filling paths created with lineTo, arc, etc.

On Thu, 8 Oct 2009, Charles Pritchard wrote:
> [...] it would work with other things; use a fillRect across the extent 
> of your clipping path. And there you go, aliased paths.

On Sun, 4 Oct 2009, Robert O'Callahan wrote:
> I would just have boolean property named "antialias".

On Thu, 8 Oct 2009, Charles Pritchard wrote:
> There are two completely different renderings for various compositon 
> modes in Chrome and Firefox. Chrome developers have certainly posted as 
> to why they chose their method. Firefox devs have certainly taken their 
> stand. I think they're both valid operations, but I'd like to have some 
> unity. [...]

On Fri, 9 Oct 2009, Robert O'Callahan wrote:
> I agree it would be good for canvas users to be able to turn off 
> antialiasing in <canvas>. But your syntax is not the best way to do 
> that. In particular, this really has nothing to do with clipping, it's 
> all about antialiasing, and a boolean property would be just fine here 
> IMHO. It doesn't matter if <canvas> currently has no boolean properties, 
> lots of other elements do.

Turning off anti-aliasing just trades one problems for another.

IT seems like what we should really do is either have UAs oversample 
without antialiasing and then downsample for rendering, or, if that is 
considered too expensive, provide primitives that make this a non-problem. 
For example, instead of just having the ability to draw rectangles, maybe 
we need the ability to specify a number of rectangles, and then have them 
all drawn at once, so that if they are adjacent, the UA can render them 
without the anti-aliasing artifacts between them.

In either case, it seems like something best handled in a future version.

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'

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