java generates pictures, add watermark

private static final String URL = "D:/test/template.png";

public static String certificateBuilder(String nickname, BigDecimal totalAmount) {

        //得到图片缓冲区
        FileInputStream fileInputStream = null;
        String savePath = "";
        try {
            File file = new File(URL);

            if (!file.exists()) {
                log.info("模板不存在");
            } else {
                fileInputStream = new FileInputStream(file);
                BufferedImage image = ImageIO.read(fileInputStream);
                BufferedImage image2 = ImageIO.read(new File("D:/test/stamp.png"));
                //获取图片的宽
                int width = image.getWidth(null);
                //获取图片的高
                int height = image.getHeight(null);
                log.info("模板位置：{}.宽：{}.高：{}.", URL, width, height);

                //初始化画板
                BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
                //得到它的绘制环境
                Graphics2D g2 = (Graphics2D) bi.getGraphics();
                g2.fillRect(0, 0, width, height);
                //设置颜色
                g2.setColor(Color.WHITE);
                // 将图片大小设置为大约4cm*4cm 具体根据纸张大小设定
                g2.drawImage(image, 0, 0, width, height, null);
                g2.drawRect(0, 0, width, height);


                g2.setFont(new Font("微软雅黑", Font.PLAIN, 30));
                g2.setColor(Color.gray);
                g2.drawString("证书编号：H11111122222233333", 315, 410);

                //设置背景颜色
                g2.setColor(Color.BLACK);
                //向图片上写字符串
                g2.setFont(new Font("微软雅黑", Font.PLAIN, 42));
                g2.drawString("大慈善家", 320, 570);
                g2.setFont(new Font("微软雅黑", Font.PLAIN, 42));
                g2.drawString("2020年9月20日", 720, 1330);
                g2.setFont(new Font("微软雅黑", Font.PLAIN, 42));
                g2.setColor(Color.RED);
                g2.drawString("5.12元", 450, 1030);

                //盖章
                g2.drawImage(image2, 810, 1174, image2.getWidth(null), image2.getHeight(null), null);

                // 合成图片
                StringBuffer path = new StringBuffer();
                path.append("D:/test/");
                path.append(UUIDUtils.gen());
                path.append("-");
                path.append(nickname);
                path.append(".png");

                boolean bool = ImageIO.write(bi, "PNG", new FileOutputStream(path.toString()));
                log.info("结果：{}.", bool);
                if (bool) {
                    savePath = path.toString();
                }
            }
        } catch (Exception e) {
            log.error("生成图片错误", e);
        } finally {
            //关流
            if (fileInputStream != null) {
                try {
                    fileInputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return savePath;
        }
    }