http://www.zeromemos.com/index/article/read.html?id=345

接着文字logo，给上面链接中的工具类加上添加logo水印的方法，完整工具类会放文末下载

    /**
     * 给图片添加水印logo
     * @param logo logo文件位置
     * @param inputStream 源图片路径
     * @param outputStream 目标图片路径
     * @param degree 水印旋转
     * @param typeName 文件后缀名
     */
    public static void markLogoImageByIO(String logo, InputStream inputStream, OutputStream outputStream,
                                     Integer degree, String typeName) {
        try {
            // 1、源图片
            Image srcImg = ImageIO.read(inputStream);

            int imgWidth = srcImg.getWidth(null);
            int imgHeight = srcImg.getHeight(null);
            BufferedImage buffImg = new BufferedImage(imgWidth, imgHeight, BufferedImage.TYPE_INT_RGB);

            // 2、得到画笔对象
            Graphics2D g = buffImg.createGraphics();

            // 3、把源图先画上
            g.drawImage(srcImg.getScaledInstance(imgWidth, imgHeight, Image.SCALE_SMOOTH), 0, 0, null);

            // 4、读取水印图片
            File fileLogo = new File(logo);
            Image imgLogo = ImageIO.read(fileLogo);

            // 5、读取水印的宽高
            int logoWidth = imgLogo.getWidth(null);
            int logoHeight = imgLogo.getHeight(null);

            // 6、设置水印旋转
            if (null != degree) {
                g.rotate(Math.toRadians(degree), (double) buffImg.getWidth() / 2, (double) buffImg.getHeight() / 2);
            }

            // 7、设置水印透明度
            g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_ATOP, alpha));

            // 8、第一参数->设置的内容，后面两个参数->文字在图片上的坐标位置(x,y)
            g.drawImage(imgLogo, imgWidth - logoWidth - 20, imgHeight - logoHeight - 20, null);
            // 9、释放资源
            g.dispose();
            // 10、生成图片
            ImageIO.write(buffImg, typeName.toUpperCase(), outputStream);

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

Controller里添加测试方法

    @Autowired
    private WaterMarkUtil waterMarkUtil;

    //图片水印
    @PostMapping("/watermark")
    public R watermark(MultipartFile photo){
        //如果非空
        if (!photo.isEmpty()){
            //获取文件名
            String originalFilename = photo.getOriginalFilename();
            //获取文件后缀
            int length = originalFilename.length();
            String typeName = originalFilename.substring(originalFilename.indexOf(".")+1, length);
            //文件保存路径
            String fileName = "C:\\Users\\admin\\Desktop\\" + originalFilename;
            File targetFile = new File(fileName);

            //水印logo文件位置
            String logo = "C:\\Users\\admin\\Desktop\\logo.png";

            InputStream inputStream = null;
            OutputStream outputStream = null;
            try {
                inputStream = photo.getInputStream();
                outputStream = new FileOutputStream(targetFile);
                //使用工具类添加水印
                waterMarkUtil.markLogoImageByIO(logo, inputStream, outputStream, 0, typeName);
                outputStream.close();
                inputStream.close();
                System.out.println("*****图片上传成功*****");
                return R.ok().data("info", "图片上传成功");
            } catch (IOException e) {
                e.printStackTrace();
            }

        }
        return R.error();
    }

测试结果如下(水印位置右下角)：