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422 Working with Geometry

Finding unions and intersections of Rectangle

objects

You use the union() method to find the rectangular region formed by the boundaries of two

rectangles:

import flash.display.*;

import flash.geom.Rectangle;

var rect1:Rectangle = new Rectangle(0, 0, 100, 100);

trace(rect1); // (x=0, y=0, w=100, h=100)

var rect2:Rectangle = new Rectangle(120, 60, 100, 100);

trace(rect2); // (x=120, y=60, w=100, h=100)

trace(rect1.union(rect2)); // (x=0, y=0, w=220, h=160)

You use the intersection() method to find the rectangular region formed by the

overlapping region of two rectangles:

import flash.display.*;

import flash.geom.Rectangle;

var rect1:Rectangle = new Rectangle(0, 0, 100, 100);

trace(rect1); // (x=0, y=0, w=100, h=100)

var rect2:Rectangle = new Rectangle(80, 60, 100, 100);

trace(rect2); // (x=120, y=60, w=100, h=100)

trace(rect1.intersection(rect2)); // (x=80, y=60, w=20, h=40)

You use the intersects() method to find out whether two rectangles intersect. You can also

use the

intersects() method to find out whether a display object is in a certain region of

the Stage. For example, in the following code, assume that the coordinate space of the display

object container that contains the

circle object is the same as that of the Stage. The example

shows how to use the

intersects() method to determine if a display object, circle,

intersects specified regions of the Stage, defined by the

target1 and target2 Rectangle

objects:

import flash.display.*;

import flash.geom.Rectangle;

var circle:Shape = new Shape();

circle.graphics.lineStyle(2, 0xFF0000);

circle.graphics.drawCircle(250, 250, 100);

addChild(circle);

var circleBounds:Rectangle = circle.getBounds(stage);

var target1:Rectangle = new Rectangle(0, 0, 100, 100);

trace(circleBounds.intersects(target1)); // false

var target2:Rectangle = new Rectangle(0, 0, 300, 300);

trace(circleBounds.intersects(target2)); // true

Similarly, you can use the intersects() method to find out whether the bounding

rectangles of two display objects overlap. You can use the

getRect() method of the

DisplayObject class to include any additional space that the strokes of a display object may

add to a bounding region.