How to draw an oval in html5 canvas?

updates:

• scaling method can affect stroke width appearance
• scaling method done right can keep stroke width intact
• canvas has ellipse method that Chrome now supports
• added updated tests to JSBin

JSBin Testing Example (updated to test other’s answers for comparison)

• Bezier – draw based on top left containing rect and width/height
• Bezier with Center – draw based on center and width/height
• Arcs and Scaling – draw based on drawing circle and scaling
  • see Deven Kalra’s answer
• Quadratic Curves – draw with quadratics
  • test appears to not draw quite the same, may be implementation
  • see oyophant’s answer
• Canvas Ellipse – using W3C standard ellipse() method
  • test appears to not draw quite the same, may be implementation
  • see Loktar’s answer

Original:

If you want a symmetrical oval you could always create a circle of radius width, and then scale it to the height you want (edit: notice this will affect stroke width appearance – see acdameli’s answer), but if you want full control of the ellipse here’s one way using bezier curves.

<canvas id="thecanvas" width="400" height="400"></canvas>

<script>
var canvas = document.getElementById('thecanvas');

if(canvas.getContext) 
{
  var ctx = canvas.getContext('2d');
  drawEllipse(ctx, 10, 10, 100, 60);
  drawEllipseByCenter(ctx, 60,40,20,10);
}

function drawEllipseByCenter(ctx, cx, cy, w, h) {
  drawEllipse(ctx, cx - w/2.0, cy - h/2.0, w, h);
}

function drawEllipse(ctx, x, y, w, h) {
  var kappa = .5522848,
      ox = (w / 2) * kappa, // control point offset horizontal
      oy = (h / 2) * kappa, // control point offset vertical
      xe = x + w,           // x-end
      ye = y + h,           // y-end
      xm = x + w / 2,       // x-middle
      ym = y + h / 2;       // y-middle

  ctx.beginPath();
  ctx.moveTo(x, ym);
  ctx.bezierCurveTo(x, ym - oy, xm - ox, y, xm, y);
  ctx.bezierCurveTo(xm + ox, y, xe, ym - oy, xe, ym);
  ctx.bezierCurveTo(xe, ym + oy, xm + ox, ye, xm, ye);
  ctx.bezierCurveTo(xm - ox, ye, x, ym + oy, x, ym);
  //ctx.closePath(); // not used correctly, see comments (use to close off open path)
  ctx.stroke();
}

</script>