drawCircle

drawCircle.as

function drawCircle( graphics:Graphics, x:Number, y:Number, radius:Number ):void
{
	var k:Number = 4 / 3 * ( Math.SQRT2 - 1 );
	var a:Number, b:Number, c:Number, d:Number, e:Number;
	var ax:Number, bx:Number, cx:Number, dx:Number, ex:Number;
	var ay:Number, by:Number, cy:Number, dy:Number, ey:Number;
	e = radius;
	d = k * radius;
	c = 0;
	b = -d;
	a = -e;
	ax = a + x;
	bx = b + x;
	cx = c + x;
	dx = d + x;
	ex = e + x;
	ay = a + y;
	by = b + y;
	cy = c + y;
	dy = d + y;
	ey = e + y;
	graphics.moveTo( cx, ay );
	graphics.cubicCurveTo( dx, ay, ex, by, ex, cy );
	graphics.cubicCurveTo( ex, dy, dx, ey, cx, ey );
	graphics.cubicCurveTo( bx, ey, ax, dy, ax, cy );
	graphics.cubicCurveTo( ax, by, bx, ay, cx, ay );
	/*
	//ccw in flash screen coordinate
	graphics.cubicCurveTo( bx, ay, ax, by, ax, cy );
	graphics.cubicCurveTo( ax, dy, bx, ey, cx, ey );
	graphics.cubicCurveTo( dx, ey, ex, dy, ex, cy );
	graphics.cubicCurveTo( ex, by, dx, ay, cx, ay );
	*/
}

drawCircleUsingQuadraticBezier.as

function drawCircleUsingQuadraticBezier( graphics:Graphics, x:Number, y:Number, radius:Number ):void
{
	var pi:Number = Math.PI;
	var a:Number, b:Number, c:Number, d:Number, e:Number, f:Number, g:Number;
	var ax:Number, bx:Number, cx:Number, dx:Number, ex:Number, fx:Number, gx:Number;
	var ay:Number, by:Number, cy:Number, dy:Number, ey:Number, fy:Number, gy:Number;
	g = radius;
	f = Math.sin( pi / 4 ) * radius;
	e = Math.tan( pi / 8 ) * radius;
	d = 0;
	c = -e;
	b = -f;
	a = -g;
	ax = a + x;
	bx = b + x;
	cx = c + x;
	dx = d + x;
	ex = e + x;
	fx = f + x;
	gx = g + x;
	ay = a + y;
	by = b + y;
	cy = c + y;
	dy = d + y;
	ey = e + y;
	fy = f + y;
	gy = g + y;
	graphics.moveTo( dx, ay );
	graphics.curveTo( ex, ay, fx, by );
	graphics.curveTo( gx, cy, gx, dy );
	graphics.curveTo( gx, ey, fx, fy );
	graphics.curveTo( ex, gy, dx, gy );
	graphics.curveTo( cx, gy, bx, fy );
	graphics.curveTo( ax, ey, ax, dy );
	graphics.curveTo( ax, cy, bx, by );
	graphics.curveTo( cx, ay, dx, ay );
}