В вашем случае, вероятно, было бы проще использовать StageScaleMode.NO_SCALE и самостоятельно кодировать изменение размера:
stage.addEventListener(Event.RESIZE, onStageResize);
private function onStageResize(event : Event) : void
{
var stageW : int = stage.stageWidth;
var stageH : int = stage.stageHeight;
var contentW : int = yourVisibleContent.width;
var contentH : int = yourVisibleContent.height;
// resize it to fit
var canvasAspectRatio : Number = stageW / stageH;
var contentAspectRatio : Number = contentW / contentH;
if(canvasAspectRatio > contentAspectRatio)
{
yourVisibleContent.height = stageH;
yourVisibleContent.width = yourVisibleContent.height * contentAspectRatio;
} else {
yourVisibleContent.width = stageW;
yourVisibleContent.height = yourVisibleContent.width / contentAspectRatio;
}
// center it:
yourVisibleContent.x = (stageW - yourVisibleContent.width) / 2;
yourVisibleContent.y = (stageH - yourVisibleContent.height) / 2;
// fill remaining space with black:
graphics.beginFill(0x000000);
if(canvasAspectRatio > contentAspectRatio)
{
var horizontalEmptySpace : Number = stageW - yourVisibleContent.width;
graphics.drawRect(0, 0, horizontalEmptySpace / 2, stageH);
graphics.drawRect(stageW - horizontalEmptySpace / 2, 0, horizontalEmptySpace / 2, stageH);
}else{
var verticalEmptySpace : Number = stageH - yourVisibleContent.height;
graphics.drawRect(0, 0, stageW, verticalEmptySpace / 2);
graphics.drawRect(0, stageH - verticalEmptySpace / 2, stageW, verticalEmptySpace / 2);
}
// now you can also redraw your bitmaps with higher resolutions
// it is easy to read the scale of your content with: yourVisibleContent.scaleX and yourVisibleContent.scaleY
}