Bitmap scaling works extremely well?

1

I’m kinda new to bitmap-related stuff…so correct me if this whole thing is not how it should be done
I was testing the quality of resizing a clip using bitmap. In some articles they say that resizing often kills the quality of a pic.
in the library, I have a mc in which I drew a tiiiiny circle, filled it with radial coloring.

var scale:Number=100;
var icircle:circle=new circle();
var bitmapData:BitmapData=new BitmapData(icircle.width*scale,icircle.height*scale);
bitmapData.draw(icircle,new Matrix(scale,0,0,scale,0,0));

var bitmap:Bitmap=new Bitmap(bitmapData);
addChild(bitmap);

the result is a huge circle with vector-like quality, I could only see the pixels when I zoom it.
I guess that flash first scale the circle in vector, THEN transform in into bitmap?

edit:

  1. if I want to move the bitmapdata before adding it to a bitmap, is Matrix the only option?

  2. what happens if I use scroll, and the bitmap goes outside the limits set by my bitmapData? Will it auto-delete itself?

  3. how do I delete part of a bitmap/bitmapData? I could always use fillRect() to set an area transparent but I don’t know if this is the right method.

thanks