Actionscript 3 Bitmap of screen selection

I have a Flash project for school and I would like to detect collision through checking to see if a pixel is black around the player. I have looked all over and I cannot seam to implement what they describe. I know that flash is capable of getting a bitmap of the screen can anyone help me?

I started searching again. And I found it

var scr:BitmapData = new BitmapData(stage.stageWidth,.stage.stageHeight);
scr.draw(stage);
var color:Number=scr.getPixel(x:int, y:int);

Sorry for the waste of DB space