// http://webreflection.blogspot.com/2009/01/ellipse-and-circle-for-canvas-2d.html
  (function(){
    // Andrea Giammarchi - Mit Style License
    var extend = {
      // Circle methods
      circle:function(aX, aY, aDiameter){
        this.ellipse(aX, aY, aDiameter, aDiameter);
      },
      fillCircle:function(aX, aY, aDiameter){
        this.beginPath();
        this.circle(aX, aY, aDiameter);
        this.fill();
      },
      strokeCircle:function(aX, aY, aDiameter){
        this.beginPath();
        this.circle(aX, aY, aDiameter);
        this.stroke();
      },
      // Ellipse methods
      ellipse:function(aX, aY, aWidth, aHeight){
        aX -= aWidth / 2;
        aY -= aHeight / 2;
        var hB = (aWidth / 2) * .5522848,
        vB = (aHeight / 2) * .5522848,
        eX = aX + aWidth,
        eY = aY + aHeight,
        mX = aX + aWidth / 2,
        mY = aY + aHeight / 2;
        this.moveTo(aX, mY);
        this.bezierCurveTo(aX, mY - vB, mX - hB, aY, mX, aY);
        this.bezierCurveTo(mX + hB, aY, eX, mY - vB, eX, mY);
        this.bezierCurveTo(eX, mY + vB, mX + hB, eY, mX, eY);
        this.bezierCurveTo(mX - hB, eY, aX, mY + vB, aX, mY);
        this.closePath();
      },
      fillEllipse:function(aX, aY, aWidth, aHeight){
        this.beginPath();
        this.ellipse(aX, aY, aWidth, aHeight);
        this.fill();
      },
      strokeEllipse:function(aX, aY, aWidth, aHeight){
        this.beginPath();
        this.ellipse(aX, aY, aWidth, aHeight);
        this.stroke();
      }
    };
  
    for(var key in extend)
      CanvasRenderingContext2D.prototype[key] = extend[key];
  })();