code: public function generateImage($filename = false, $level = Constants::QR_ECLEVEL_L, $size = 3, $margin = 4)
      {
          $result = 'SPD' . self::DELIMITER . $this->version . self::DELIMITER . $this->implodeContent();
  
          if ($this->appendCRC32) {
              $result .= self::DELIMITER . 'CRC32:' . sprintf('%x', crc32($result));
          }
  
          QRcode::png($result, $filename, $level, $size, $margin);
          die();
      }
docs: Generate SPD as PNG image and output it
  
  @param string|bool $filename Image filename
  @param int $level QR code error correction level - please see Constants::QR_ECLEVEL_*
  @param int $size QR code size (1 - 1024)
  @param int $margin QR code margin