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Please consider elliptical arc in canvas

From: Shaofei Cheng <csf178@163.com>
Date: Sun, 13 Nov 2011 19:27:00 +0800 (CST)
To: public-canvas-api@w3.org
Message-ID: <5b22465e.4239.1339cae2bc4.Coremail.csf178@163.com>
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 )




Thanks,
Shaofei Cheng
Received on Sunday, 13 November 2011 20:35:53 GMT

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