Currently, when generating QR codes with DNS2D::getBarcodePNG(), the PNG output has a transparent background by default. It would be useful to allow specifying a background color directly during generation, to avoid additional GD processing.

Expected behavior:

The function should accept a new optional parameter for background color:
$png = DNS2D::getBarcodePNG($code, $type, $width, $height, $color, $backgroundColor);

Generated PNG should have the specified background color (default: transparent if not provided).

Use case / Benefit:

• Avoids having to post-process PNGs with GD to add a white background.

• Useful for printing, marketing campaigns, or when transparent PNGs are not supported.