// Create new configuration that specifies the error correction
Map<EncodeHintType, ErrorCorrectionLevel> hints = new HashMap<EncodeHintType, ErrorCorrectionLevel>();
hints.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.H);

QRCodeWriter writer = new QRCodeWriter();
BitMatrix bitMatrix = null;
ByteArrayOutputStream baos = new ByteArrayOutputStream();

try {
    // Create a qr code with the url as content and a size of 250x250 px
    bitMatrix = writer.encode("http://www.wombatsoftware.de", BarcodeFormat.QR_CODE, 250, 250, hints);

    MatrixToImageConfig config = new MatrixToImageConfig(MatrixToImageConfig.BLACK, MatrixToImageConfig.WHITE);

    // Load QR image
    BufferedImage qrImage = MatrixToImageWriter.toBufferedImage(bitMatrix, config);

    // Load logo image
    BufferedImage logoImage = ImageIO.read(request.getSession().getServletContext().getResourceAsStream("/images/logo.png"));

    // Calculate the delta height and width between QR code and logo
    int deltaHeight = qrImage.getHeight() - logoImage.getHeight();
    int deltaWidth = qrImage.getWidth() - logoImage.getWidth();

    // Initialize combined image
    BufferedImage combined = new BufferedImage(qrImage.getHeight(), qrImage.getWidth(), BufferedImage.TYPE_INT_ARGB);
    Graphics2D g = (Graphics2D) combined.getGraphics();

    // Write QR code to new image at position 0/0
    g.drawImage(qrImage, 0, 0, null);
    g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 1f));

    // Write logo into combine image at position (deltaWidth / 2) and
    // (deltaHeight / 2). Background: Left/Right and Top/Bottom must be
    // the same space for the logo to be centered
    g.drawImage(logoImage, (int) Math.round(deltaWidth / 2), (int) Math.round(deltaHeight / 2), null);

    // Write combined image as PNG to OutputStream
    ImageIO.write(combined, "png", baos);
} catch (WriterException e) {
    LOG.error("WriterException occured", e);
} catch (IOException e) {
    LOG.error("IOException occured", e);
}

// Do something with the OutputStream