private function getThumbnailBaseFolderPaths()
    {
        if (is_array($this->thumbnailBaseDir)) {
            return $this->thumbnailBaseDir;
        }

        $this->thumbnailBaseDir = [];

        if (null !== $baseFolder = $this->getBaseFolder()) {
            $thumbnailBaseDir = array_map(function ($directory) use ($baseFolder) {
                return str_replace(
                    DIRECTORY_SEPARATOR.DIRECTORY_SEPARATOR,
                    DIRECTORY_SEPARATOR,
                    $directory.DIRECTORY_SEPARATOR.$baseFolder
                );
            }, $this->application->getResourceDir());

            foreach (array_unique($thumbnailBaseDir) as $directory) {
                if (is_dir($directory)) {
                    $this->thumbnailBaseDir[] = $directory;
                }
            }
        }

        return $this->thumbnailBaseDir;
    }