自己写的，觉得非常简单经典。java给图片添加文子或者水印都需要用到。

try{
String fileName = "D:/certificate.jpg";// 源图路径  
                String outFileName = "D:/test.jpg";// 新生成图片路径  
                FileInputStream fis = new FileInputStream(fileName);
                BufferedImage outImg = ImageIO.read(fis);
                
                Graphics g = outImg.getGraphics();
                g.setFont(new Font("Times New Roman",Font.ROMAN_BASELINE,18));
                g.setColor(new Color(102,102,102));  //设字体为黑色,否则就是白色
                g.drawString("houyongsssssss", 100, 215);
                g.dispose();//保存修改
                FileOutputStream outPictrue = new FileOutputStream(outFileName); 
                ImageIO.write(outImg, "JPEG", outPictrue);
                } catch (FileNotFoundException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                }