code: protected Bitmap.Config preferredBitmapConfig() {
      ActivityManager activityManager = (ActivityManager)
        getApplication().getSystemService(Context.ACTIVITY_SERVICE);
      int memoryClass = activityManager.getMemoryClass();
      int format = getWindowManager().getDefaultDisplay().getPixelFormat();
      // for low memory devices (like the HTC Magic), prefer 16-bit bitmaps
      return (format == PixelFormat.RGBA_4444 || memoryClass <= 16) ?
        Bitmap.Config.ARGB_4444 : Bitmap.Config.ARGB_8888;
    }
docs: Returns the configuration that will be used to decode bitmaps. The default implementation uses
  {@code ARGB_8888} unless the device memory class is 16MB or less or the device screen is
  itself {@code ARGB_4444}. NOTE: this is called once during platform initialization and the
  result is used for the lifetime of the game.