Wrote a function to center image it works, it maybe a starting point for you so that you can write your own function. using 4.01
public var oldImage:String; private function centerImage(rImage:Image):void { var capImg:Image = new Image(); var newImage:Bitmap = new Bitmap(); var ch:Number = 0; var cw:Number = 0; var ih:Number = 0; var iw:Number = 0; var mX:Number = 0; var mY:Number = 0; capImg = rImage; /* the following is to reduce the image flicker in a list using an itemrenderer*/ if (oldImage != null && capImg.source == oldImage) return; else oldImage = String(capImg.source); newImage = new Bitmap(Bitmap(capImg.content).bitmapData); ch = HEIGHTNUMBER; cw = WIDTHNUMBER; ih = capImg.content.height; iw = capImg.content.width; if (ih> iw){ cw = iw*ch/ih; } else if (ih<iw){ ch = ih*cw/iw; } mX = (WIDTHNUMBER - cw) /2; mY = (HEIGHTNUMBER - ch) /2; capImg.x = mX; capImg.y = mY; capImg.width = cw; capImg.height = ch; capImg.source = newImage; }