public function generate($text, $filename = null)
{
$qrCode = $this->writer->writeString($text, $this->encoding, $this->errorCorrection);
if ($this->imageMerge !== null) {
$merger = new ImageMerge(new Image($qrCode), new Image($this->imageMerge));
$qrCode = $merger->merge($this->imagePercentage);
}
if ($filename === null) {
return $qrCode;
} else {
file_put_contents($filename, $qrCode);
}
}