QR Code PNGs Render with Only Borders (No Fill) in TCPDF

[eugenio11]

For some reasons, I am required to use GDLibRenderer, that, despite its limits, seems to work well with simple QR Codes displayed in a Web page.

However, if I embed them in a PDF via the TCPDF library, the QR codes appear with only outlines and no filled black modules — rendering them unreadable. Strangely, switching the format to 'gif':

new GDLibRenderer($qrcode_size, 4, 'gif');
resolves the issue (though blurry), suggesting that the root cause is maybe transparency? Any suggestion to solve this issue?

Thanks in advance for any help or clarification!

[DASPRiD]

That doesn't really sound like an issue with the image itself to me. If the image is blurry, that'd usually mean that it's resolution is too low. Although I know that sometimes PDF renderers also render things in a weird way at certain scales.

[ThibDel8]

Be careful with unit conversions: I belive TCPDF uses millimeters by default, while Bacon uses pixels.

You can convert like this :

private function qrSize(int $sizeMm): int
{
return (int) round($sizeMm / 25.4 * 72);
}