How to generate qr code with Image overlay in Gluon?

Question

I want to generate QR CODE which have to put logo in the center. I have check the zxing library and I did it with a Java application by reading this code (How to generate QR code with logo inside it?). But as I know we can't use swing in android/ios. So how to deal with this ?

Answer 1

Based on the link you are referring, the accepted answer pointed to this post, where you can see that the trick to generate a QR that allows hiding its center part without affecting its readability by a QR scanner, can be done by increasing the error level:

30% (H) of error correction were a error correction of level H should result in a QRCode that is still valid even when it’s 30% obscured

As a follow-up of this question, you can just include a hint when encoding the text:

public Image generateQR(int width, int height) {
    File root = Services.get(StorageService.class)
            .flatMap(StorageService::getPrivateStorage)
            .orElseThrow(() -> new RuntimeException("Storage Service not found"));

    String uuid = Services.get(DeviceService.class)
            .map(DeviceService::getUuid)
            .orElse("123456789");

    MultiFormatWriter codeWriter = new MultiFormatWriter();

    // Add maximum correction
    Map<EncodeHintType, ErrorCorrectionLevel> hints = new HashMap<>();
    hints.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.H);

    try {
        BarcodeFormat format = BarcodeFormat.QR_CODE;
        BitMatrix bitMatrix = codeWriter.encode(uuid, format, 
               width, height, hints);  // <--- add hints
        ...
        return writableImage;
    }
}

You will be getting a QR code image, without overlay.

The next step is to combine this image with your logo image, without using Swing. But we actually don't need to do that: we can just use two ImageView nodes!

ImageView imageView = new ImageView();
imageView.setFitWidth(256);
imageView.setFitHeight(256);
imageView.setImage(service.generateQR(256, 256));

ImageView overlay = new ImageView(
     new Image(getClass().getResourceAsStream("/icon.png")));
overlay.setFitWidth(80);
overlay.setFitHeight(80);

StackPane combinedQR = new StackPane(imageView, overlay);
...

The resulting code is still readable.

You can also play with the result, adding a blend effect to the images, like:

overlay.setBlendMode(BlendMode.ADD);

but this will depend on how your logo image blends with the QR.

Finally, if you still need a single combined image, you can create a snapshot of the stack pane:

WritableImage snapshot = combinedQR.snapshot(new SnapshotParameters(), null);