boundingBox.as

import flash.events.Event;
import flash.geom.Point;
import flash.geom.Matrix;

var N:uint = 4;
var speed:uint = 1;
var marks:Vector.<Mark> = new Vector.<Mark>(N, true);
var vertices:Vector.<Point> = new Vector.<Point>(N, true);
var center:Point = new Point(rect.x, rect.y);
var matrix:Matrix = new Matrix();
var r:uint = 0;

var i:uint;

vertices[0] = new Point(rect.x, rect.y);
vertices[1] = new Point(rect.x + rect.width, rect.y);
vertices[2] = new Point(rect.x + rect.width, rect.y + rect.height);
vertices[3] = new Point(rect.x, rect.y + rect.height);

matrix.translate(-(rect.width * .5), -(rect.height * .5));

for (i = 0; i < N; i++) {
	vertices[i] = matrix.transformPoint(vertices[i]);
	marks[i] = new Mark();
	marks[i].x = vertices[i].x;
	marks[i].y = vertices[i].y;
	addChild(marks[i]);
}

function drawBoundingBox():void
{
	const quadrant:uint = Math.floor(r / 90);
	const X:int = vertices[(3 - quadrant + N) % N].x;
	const Y:int = vertices[(0 - quadrant + N) % N].y;
	const W:int = vertices[(1 - quadrant + N) % N].x - X;
	const H:int = vertices[(2 - quadrant + N) % N].y - Y;
	
	graphics.clear();
	graphics.lineStyle(1);
	graphics.drawRect(X, Y, W, H);
}

addEventListener(Event.ENTER_FRAME, function(event:Event):void
{
	rect.rotation += speed;
	
	matrix = new Matrix();
	matrix.translate(-center.x, -center.y);
	matrix.rotate(speed * 2 * Math.PI / 360);
	matrix.translate(center.x, center.y);
	
	for (i = 0; i < N; i++) {
		vertices[i] = matrix.transformPoint(vertices[i]);
		marks[i].x = vertices[i].x;
		marks[i].y = vertices[i].y;
	}
	
	r = (r + speed) % 360;
	drawBoundingBox();
});

boundingBoxWithLookup.as

import flash.events.Event;
import flash.geom.Point;
import flash.geom.Matrix;

var N:uint = 4;
var speed:uint = 1;
var marks:Vector.<Mark> = new Vector.<Mark>(N, true);
var vertices:Vector.<Point> = new Vector.<Point>(N, true);
var center:Point = new Point(rect.x, rect.y);
var matrix:Matrix = new Matrix();

var i:uint;

vertices[0] = new Point(rect.x, rect.y);
vertices[1] = new Point(rect.x + rect.width, rect.y);
vertices[2] = new Point(rect.x + rect.width, rect.y + rect.height);
vertices[3] = new Point(rect.x, rect.y + rect.height);

matrix.translate(-(rect.width * .5), -(rect.height * .5));

for (i = 0; i < N; i++) {
	vertices[i] = matrix.transformPoint(vertices[i]);
	marks[i] = new Mark();
	marks[i].x = vertices[i].x;
	marks[i].y = vertices[i].y;
	addChild(marks[i]);
}

const LOOKUP:Vector.<Vector.<uint>> = new <Vector.<uint>>[
	new <uint>[3, 0, 1, 2],
	new <uint>[2, 3, 0, 1],
	new <uint>[1, 2, 3, 0],
	new <uint>[0, 1, 2, 3],
];

function normalizeRotation(rotation:int):int
{
	return (rotation + 360) % 360;
}

function drawBoundingBox():void
{
	const quadrant:uint = (normalizeRotation(rect.rotation) / 90) >> 0;
	const T:Vector.<uint> = LOOKUP[quadrant];
	const X:int = vertices[T[0]].x;
	const Y:int = vertices[T[1]].y;
	const W:int = vertices[T[2]].x - X;
	const H:int = vertices[T[3]].y - Y;
	
	graphics.clear();
	graphics.lineStyle(1);
	graphics.drawRect(X, Y, W, H);
}

addEventListener(Event.ENTER_FRAME, function(event:Event):void
{
	rect.rotation += speed;
	
	matrix = new Matrix();
	matrix.translate(-center.x, -center.y);
	matrix.rotate(speed * 2 * Math.PI / 360);
	matrix.translate(center.x, center.y);
	
	for (i = 0; i < N; i++) {
		vertices[i] = matrix.transformPoint(vertices[i]);
		marks[i].x = vertices[i].x;
		marks[i].y = vertices[i].y;
	}
	
	drawBoundingBox();
});