点的旋转

/** 
 * target绕center旋转
 */
function rotatePoint(target: Point, center: Point, angle: Number): Point {
	var temp: Point = new Point();

	var ca: Number = Math.cos(angle * (Math.PI / 180));
	var sa: Number = Math.sin(angle * (Math.PI / 180));
	var xdis: Number = target.x - center.x;
	var ydis: Number = target.y - center.y;
	temp.x = center.x + ca * xdis - sa * ydis;
	temp.y = center.y + sa * xdis + ca * ydis;
/*
	var matrix: Matrix = new Matrix(1, 0, 0, 1, target.x - center.x, target.y - center.y);
	matrix.rotate(angle * Math.PI / 180);
	temp.x = center.x + matrix.tx;
	temp.y = center.y + matrix.ty;
*/
	return temp;
}