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Re: Please consider elliptical arc in canvas

From: Shaofei Cheng <csf178@163.com>
Date: Mon, 14 Nov 2011 10:37:25 +0800 (CST)
To: "Charles Pritchard" <chuck@jumis.com>
Cc: "public-canvas-api@w3.org" <public-canvas-api@w3.org>
Message-ID: <7758a07a.a66a.1339fefb007.Coremail.csf178@163.com>
That will be fine.
But if a  drawPath-style API is added and "A" command is supported, I think still the ellipse arc api is needed to to keep the two API set of path align.

At 2011-11-14 04:47:33,"Charles Pritchard" <chuck@jumis.com> wrote:

There seems to be consensus that a drawPath-style method can be added to Canvas 2d. So you'd no longer need an svg path implementation.

Would that sufficiently address the issue?


On Nov 13, 2011, at 3:27 AM, "Shaofei Cheng" <csf178@163.com> wrote:

Hey guys,
These days I'm working on a simple wrapping of canvas and just noticed that canvas leaks of elliptical canvas.arc APIs for path.

What I want to implement is like the following:

    var canvas = new CanvasWraper(myCanvas);
    canvas.drawPath("M200,300 Q400,50 600,300 T1000,300");

The main purpose is to draw a path in canvas in SVG grammar. Everything goes well except the "A" command. Canvas 2d context do not have a API for arc of ellipse. So in the following picture(which is a sample of SVG). The left graph could be draw with canvas but the right could not.
This path grammar is also supported by silverlight. 

So I suggest to add a elliptical arc API for path. With that we can keep the feature align with SVG.Also I think elliptical arc could be useful for some graphics games. 

(We are able to approx elliptical arc with cubic bezer, but I think the algorithm is too complex for web developers )

Shaofei Cheng
Received on Monday, 14 November 2011 02:37:55 UTC

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