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<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" >
<head>
<title>Approximation of an arc with bezier</title>
<style type="text/css">
        @import "../../../dojo/resources/dojo.css";
        @import "../../../dijit/tests/css/dijitTests.css";
</style>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<script type="text/javascript" src="../../../dojo/dojo.js" djConfig="isDebug: true"></script>
<script type="text/javascript" src="../_base.js"></script>
<script type="text/javascript" src="../shape.js"></script>
<script type="text/javascript" src="../path.js"></script>
<script type="text/javascript" src="../arc.js"></script>
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<!--<script type="text/javascript" src="../canvas.js"></script>-->
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<script type="text/javascript">
dojo.require("dojox.gfx");

makeShapes = function(){
        var surface = dojox.gfx.createSurface("test", 500, 300);
        var g = surface.createGroup();
        
        // create a reference ellipse
        var rx = 200;
        var ry = 100;
        var startAngle = -30;
        var arcAngle = -90;
        var axisAngle = -30;
        var e = g.createEllipse({rx: rx, ry: ry}).setStroke({});
        
        // calculate a bezier
        var alpha = dojox.gfx.matrix._degToRad(arcAngle) / 2; // half of our angle
        var cosa  = Math.cos(alpha);
        var sina  = Math.sin(alpha);
        // start point
        var p1 = {x: cosa, y: sina};
        // 1st control point
        var p2 = {x: cosa + (4 / 3) * (1 - cosa), y: sina - (4 / 3) * cosa * (1 - cosa) / sina};
        // 2nd control point (symmetric to the 1st one)
        var p3 = {x: p2.x, y: -p2.y};
        // end point (symmetric to the start point)
        var p4 = {x: p1.x, y: -p1.y};
        
        // rotate and scale poins as appropriate
        var s = dojox.gfx.matrix.normalize([dojox.gfx.matrix.scale(e.shape.rx, e.shape.ry), dojox.gfx.matrix.rotateg(startAngle + arcAngle / 2)]);
        p1 = dojox.gfx.matrix.multiplyPoint(s, p1);
        p2 = dojox.gfx.matrix.multiplyPoint(s, p2);
        p3 = dojox.gfx.matrix.multiplyPoint(s, p3);
        p4 = dojox.gfx.matrix.multiplyPoint(s, p4);
        // draw control trapezoid
        var t = g.createPath().setStroke({color: "blue"});
        t.moveTo(p1.x, p1.y);
        t.lineTo(p2.x, p2.y);
        t.lineTo(p3.x, p3.y);
        t.lineTo(p4.x, p4.y);
        t.lineTo(p1.x, p1.y);
        t.moveTo((p1.x + p4.x) / 2, (p1.y + p4.y) / 2);
        t.lineTo((p2.x + p3.x) / 2, (p2.y + p3.y) / 2);
        t.moveTo((p1.x + p2.x) / 2, (p1.y + p2.y) / 2);
        t.lineTo((p3.x + p4.x) / 2, (p3.y + p4.y) / 2);
        // draw a bezier
        var b = g.createPath().setStroke({color: "red"});
        b.moveTo(p1.x, p1.y);
        b.curveTo(p2.x, p2.y, p3.x, p3.y, p4.x, p4.y);
        // move everything in a middle
        g.setTransform([dojox.gfx.matrix.translate(250, 150), dojox.gfx.matrix.rotateg(axisAngle)]);
};

dojo.addOnLoad(makeShapes);

</script>
</head>
<body>
<h1>Approximation of an arc with bezier</h1>
<!--<p><button onclick="makeShapes();">Make</button></p>-->
<div id="test" style="width: 500px; height: 300px;"></div>
<p>That's all Folks!</p>
</body>
</html>