use fs class member

        $pathInfo = pathinfo($publicationFile->getData('path'));

        $imagePath = $pathInfo['dirname'] . DIRECTORY_SEPARATOR . $pathInfo['filename'] . DIRECTORY_SEPARATOR . $imgName;

        $fs = Services::get('file')->fs;

        $mimetype = $file->mimetype ?? 'application/octet-stream';

        $filesize = $fs->fileSize($imagePath);

        $filesize = $this->fs->fileSize($imagePath);

        $encodedFilename = urlencode($imgName);

        header("Content-Type: {$mimetype}");

        header("Content-Length: {$filesize}");

        header('Content-Disposition: inline' . ";filename=\"{$encodedFilename}\";filename*=UTF-8''{$encodedFilename}");

        header('Cache-Control: private'); // Workarounds for IE weirdness

        header('Pragma: public');

        fpassthru($fs->readStream($imagePath));

        fpassthru($this->fs->readStream($imagePath));

        exit;