代码如下：

	//set background scene
	bgmap = Sprite::create(PASTE.PNG);
	bgmap->setPosition(VisibleRect::center());//这句自己根据需要修改
	Size mywinsize=Director::getInstance()->getWinSize();
	float winw = mywinsize.width; //获取屏幕宽度
	float winh = mywinsize.height;//获取屏幕高度
	float spx = bgmap->getTextureRect().getMaxX();
	float spy = bgmap->getTextureRect().getMaxY();
	bgmap->setScaleX(winw/spx); //设置精灵宽度缩放比例
	bgmap->setScaleY(winh/spy);
	this->addChild(bgmap);