WPF 背景平铺

<Window.Background>
     <VisualBrush TileMode="Tile" Viewport="0,0,0.5,0.5">
      <VisualBrush.Visual>
        <Image Source="image.png"></Image>
      </VisualBrush.Visual>
     </VisualBrush>

</Window.Background>

注意哦：Viewport后两个数字很重要哦。