protected function buildThumbnails($files)
    {
        $thumbnails = [];

        foreach ($files as $file) {
            if (file_can_have_thumbnail($file)) {
                $thumbnails[$file] = (string) $this->image
                    ->make(Storage::get($file))
                    ->resize(20, 20)->encode('data-url');
            }
        }

        return $thumbnails;
    }