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AS3 Animation using Blitting

/ Published in: ActionScript 3
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  1. package 
  2. {    
  3.     import flash.display.Bitmap;
  4.     import flash.display.BitmapData;
  5.     import flash.display.Sprite;
  6.     import flash.events.Event;
  7.     import flash.geom.Point;
  8.     import flash.geom.Rectangle;
  9.  
  10.     // Here we declare the properties of our SWF.
  11.     [SWF(width="100", height="100", frameRate="20", backgroundColor="0x330066", quality="high", scale="noscale")] 
  12.     public class Main extends Sprite 
  13.     {        
  14.         [Embed(source = "../img/plane.png")] public var Plane:Class; //Take the image plane.png (it contains 3 frames at 32x32) and put it in the Class "Plane".
  15.         private var PlaneBmp:Bitmap = new Plane();    //Crate a new Bitmap from it.
  16.         private var FinalPlaneBmp:Bitmap = new Bitmap(); //Create an empty Bitmap.
  17.         private var PlaneAnimationArr:Array = new Array();
  18.  
  19.         private var frameNumber:int; //Here we store the current frame number for blitting.
  20.         private var point: Point = new Point(0, 0); //Anchor point, is usually 0,0.
  21.         private var rect:Rectangle = new Rectangle(0, 0, 32, 32); //The rectangle that cut the section of the image that we need.
  22.  
  23.         public function Main():void {
  24.             if (stage) init();
  25.             else addEventListener(Event.ADDED_TO_STAGE, init);
  26.         }
  27.  
  28.         private function init(e:Event = null):void {
  29.             removeEventListener(Event.ADDED_TO_STAGE, init);
  30.             addEventListener(Event.ENTER_FRAME, update); 
  31.             addChild(FinalPlaneBmp); //Let's add the empty Bitmap on the stage.
  32.             FinalPlaneBmp.smoothing = true;
  33.             FinalPlaneBmp.bitmapData = new BitmapData(32, 32); //Fill it's bitmapData with an image 32x32.
  34.             for (var i:int = 0; i < 3; i++) {
  35.                 rect.x = 32 * i; //Shift the rectangle position of 32 every frame, for 3 frames in loop.
  36.                 PlaneAnimationArr.push(new BitmapData(32, 32)); // Create a new BitmapData in the Array.
  37.                 PlaneAnimationArr[i].copyPixels(PlaneBmp.bitmapData, rect, point); //Copy the images that is under the rectangle at that position of the PlaneBmp and copy it in the Array.
  38.             }
  39.             FinalPlaneBmp.x = 50;
  40.             FinalPlaneBmp.y = 50;
  41.         }
  42.  
  43.         private function update(e:Event):void {            
  44.             frameNumber++;
  45.             if (frameNumber >= 3) frameNumber = 0;            
  46.             FinalPlaneBmp.bitmapData = PlaneAnimationArr[frameNumber];            
  47.             FinalPlaneBmp.rotation++;
  48.         }        
  49.     }    
  50. }

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