private function initializeTempDirectory()
    {
        $this->dir = __DIR__.'/.wallpaperNotifier';

        if (!file_exists($this->dir)) {
            try {
                mkdir($this->dir);
            } catch (Exception $e) {
                throw new \RuntimeException(sprintf(
                    "Wallpaper notifier requires a directory to hold its contents\n"
                    ."'%s' directory couldn't be created",
                    $this->dir
                ));
            }
        }

        // Hack: two different images are needed to reload the desktop background
        // One holds the current wallpaper, the other one is the new background
        // If you have just one image and modify it, the OS doesn't reload it
        $this->evenBackgroundImagePath = realpath($this->dir).'/even-background.png';
        $this->oddBackgroundImagePath  = realpath($this->dir).'/odd-background.png';
    }