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Bitmapdata “timelapsed snapshots” from Camera

November 24, 2009


In the actionscript coding done here, I have figured out how to display  timelapsed snapshots from my webcam. The snapshots are are displayed in a bitmap object on the stage and every one second, a new image comes up. Actually in this case I displayed two bitmaps and their one second cycles are offset by 0.5 second. This makes one of the images on stage update every 0.5 seconds (alternating). What I hope to get out of doing this code is to further code to compare one older image with one newer image, but that will be a later post hopefully.

I tested out the code by counting on my fingers to see if the bitmap images update in sequential order. I found that when counting, a new number might appear on the second image spot before it showed up on the first. I realized that this was a matter of relativity.  As soon as a new image from the video is drawn to the bitmap image located on stage, it is immediately visible. Therefore if each bitmap is redrawn in 1 second cycles and the cycles of the two bitmap are offset by half a second, then every half a second: one of the two images on stage will be updated. This means, that the newest image will alternate between bitmaps.

The actionscript code is shown below (copying & pasting in to Flash and autoformating makes it easier to read). Comments and questions are welcome!

package bitmapCamCode{
import flash.display.MovieClip;
import flash.display.BitmapData;
import flash.display.Bitmap;
import flash.utils.Timer;

public class BitmapCam extends MovieClip {

private var cam:Camera;
private var vid:Video;
private var older:BitmapData; //first frame
private var newer:BitmapData; //second frame
private var timer0:Timer;
private var timer1:Timer;
private var bmpOld:Bitmap;
private var bmpNew:Bitmap;

public function BitmapCam() {
trace("cam width = "+cam.width);
trace("cam height = "+cam.height);
vid=new Video();
var moveY:Number = 240;


// 3 second (3000 ms) delay to allow for User to Accept Camera Dialog Box
timer0= new Timer(3000, 1);
timer0.addEventListener(TimerEvent.TIMER, startLag1);

// timer 1 offsets your snapshots by 500 milliseconds
timer1= new Timer(3500, 1);
timer1.addEventListener(TimerEvent.TIMER, startLag2);

older = new BitmapData(vid.width, vid.height); //holds the data of your first snapshot
bmpOld= new Bitmap(); //bitmap to place on stage and display bitmap data
addChild(bmpOld); //placing bitmap on stage
bmpOld.bitmapData=older; //bmp on stage displays the value of Bitmapdata

newer = new BitmapData(vid.width, vid.height);
bmpNew= new Bitmap();
bmpNew.x= 320; //moving bitmap on stage
bmpNew.bitmapData=newer; //bitmap (bmpNew) will display bitmapdata(newer)

} //BitmapCam()

private function startLag1 (e:TimerEvent) //triggers the capture of the first snapshot
var timer2:Timer = new Timer(1000, 0);
timer2.addEventListener(TimerEvent.TIMER, getOldFrame);
timer0.removeEventListener(TimerEvent.TIMER, startLag1);
} //startLag1()

private function startLag2 (e:TimerEvent) //triggers the capture of the second snapshot
var timer3:Timer = new Timer(1000, 0);
timer3.addEventListener(TimerEvent.TIMER, getNewFrame);
timer1.removeEventListener(TimerEvent.TIMER, startLag2);
} //startLag2()

private function getOldFrame(e:TimerEvent)

older.draw(vid); // inputs current frame of video into Bitmapdata

} //getOldFrame()

private function getNewFrame(e:TimerEvent)


} //getNewFrame()


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