import ch.codeblock.qrinvoice.OutputFormat;
import ch.codeblock.qrinvoice.QrInvoiceCodeCreator;
import ch.codeblock.qrinvoice.model.QrInvoice;
import ch.codeblock.qrinvoice.model.builder.QrInvoiceBuilder;

import java.time.LocalDate;
import java.time.Month;

// ..

final QrInvoice qrInvoice = // create using QrInvoiceBuilder;

// the resulting byte array contains the Swiss QR Code as PNG
// please note that the size (pixels) varies
final byte[] qrCode = QrInvoiceCodeCreator
    .create()
    .qrInvoice(qrInvoice)
    .outputFormat(OutputFormat.PNG)
    .desiredQrCodeSize(500)
    .createQrCode();