Android Drawable 转化为 Bitmap

  if (drawable instanceof NinePatchDrawable) {
   NinePatchDrawable npd = (NinePatchDrawable) drawable;
   Bitmap output_bitmap = Bitmap.createBitmap(npd.getIntrinsicWidth(), npd.getIntrinsicHeight(), Bitmap.Config.ARGB_8888);
      Canvas canvas = new Canvas(output_bitmap);
      npd.draw(canvas);

      return output_bitmap;

  } else {
   BitmapDrawable bd = (BitmapDrawable) drawable;
   return bd.getBitmap();
  }