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A
Point
object defines a Cartesian pair
of coordinates. It represents location in a two-dimensional coordinate
system, where
x
represents the horizontal axis and
y
represents
the vertical axis.
To define a Point object, you set its
x
and
y
properties,
as follows:
import flash.geom.*;
var pt1:Point = new Point(10, 20); // x == 10; y == 20
var pt2:Point = new Point();
pt2.x = 10;
pt2.y = 20;
Finding the distance between two points
You can use the
distance()
method
of the Point class to find the distance between two points in a
coordinate space. For example, the following code finds the distance
between the registration points of two display objects,
circle1
and
circle2
,
in the same display object container:
import flash.geom.*;
var pt1:Point = new Point(circle1.x, circle1.y);
var pt2:Point = new Point(circle2.x, circle2.y);
var distance:Number = Point.distance(pt1, pt2);
Translating coordinate spaces
If two display objects are in
different display object containers, they can be in different coordinate
spaces. You can use the
localToGlobal()
method
of the DisplayObject class to translate the coordinates to the same
(global) coordinate space, that of the Stage. For example, the following
code finds the distance between the registration points of two display
objects,
circle1
and
circle2
, in
the different display object containers:
import flash.geom.*;
var pt1:Point = new Point(circle1.x, circle1.y);
pt1 = circle1.localToGlobal(pt1);
var pt2:Point = new Point(circle2.x, circle2.y);
pt2 = circle2.localToGlobal(pt2);
var distance:Number = Point.distance(pt1, pt2);
Similarly, to find the distance of the registration point of
a display object named
target
from a specific point
on the Stage, use the
localToGlobal()
method of
the DisplayObject class:
import flash.geom.*;
var stageCenter:Point = new Point();
stageCenter.x = this.stage.stageWidth / 2;
stageCenter.y = this.stage.stageHeight / 2;
var targetCenter:Point = new Point(target.x, target.y);
targetCenter = target.localToGlobal(targetCenter);
var distance:Number = Point.distance(stageCenter, targetCenter);
Moving a display object by a specified angle and distance
You can use the
polar()
method
of the Point class to move a display object a specific distance
by a specific angle. For example, the following code moves the
myDisplayObject
object
100 pixels by 60°:
import flash.geom.*;
var distance:Number = 100;
var angle:Number = 2 * Math.PI * (90 / 360);
var translatePoint:Point = Point.polar(distance, angle);
myDisplayObject.x += translatePoint.x;
myDisplayObject.y += translatePoint.y;
Other uses of the Point class
You
can use Point objects with the following methods and properties:
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Class
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Methods or properties
|
Description
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DisplayObjectContainer
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areInaccessibleObjectsUnderPoint()getObjectsUnderPoint()
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Used to return a list of objects under a
point in a display object container.
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BitmapData
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hitTest()
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Used to define the pixel in the BitmapData object
as well as the point that you are checking for a hit.
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BitmapData
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applyFilter()
copyChannel()
merge()
paletteMap()
pixelDissolve()
threshold()
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Used to define the positions of rectangles
that define the operations.
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Matrix
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deltaTransformPoint()
transformPoint()
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Used to define points for which you want
to apply a transformation.
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Rectangle
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bottomRight
size
topLeft
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Used to define these properties.
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