在Flex中限制模态弹出窗口的大小？

private function tileList_itemClick2(evt:ListEvent):void {
                img = new Image();
                    img.maintainAspectRatio = true;
                    img.addEventListener(Event.COMPLETE, image_complete);
                    img.addEventListener(ResizeEvent.RESIZE, image_resize);
                    img.addEventListener(MouseEvent.CLICK, image_click);           

                    img.source = "products/images/" + evt.itemRenderer.data.imgH;
                    img.setStyle("addedEffect", image_addedEffect);
                    img.setStyle("removedEffect", image_removedEffect);
                    PopUpManager.addPopUp(img, myCanvas, true); 
             }
private function tileList_itemClick2(evt:ListEv