ShapeTest.as

var backTexture:SubTexture = atlas.getTexture("menuBackground") as SubTexture;
var clipping:Rectangle = backTexture.clipping;
var uvMatrix:Matrix = new Matrix();
uvMatrix.scale(stage.stageWidth / (backTexture.width * clipping.width), stage.stageHeight / (backTexture.height * clipping.height));

var background:Shape = new Shape();
addChild(background);
background.graphics.beginTextureFill(backTexture, uvMatrix);
background.graphics.drawRect(0, 0, stage.stageWidth, stage.stageHeight);
background.graphics.endFill();