如何用java给图片添加图片水印（透明度、旋转、居中）？javaqq39380155的博客-

最近在做一个食品溯源项目，需要对一些图片加上水印。
注释都在代码里了，有啥想法可以在评论区交流(๑•ᴗ•๑)~

 // 水印透明度 private static float alpha = 0.5f; /**      * 给图片添加水印图片、可设置水印图片旋转角度      *      * @param iconPath   水印图片路径      * @param srcImgPath 源图片路径      * @param location   水印图片位置      * @param degree     水印图片旋转角度      */ public static void markImageByIcon(HttpServletRequest request, HttpServletResponse response,                                        String iconPath, String srcImgPath, String location, Integer degree) {         OutputStream os = null; try {              Image srcImg = ImageIO.read(new File(srcImgPath));              BufferedImage buffImg = new BufferedImage(srcImg.getWidth(null),                     srcImg.getHeight(null), BufferedImage.TYPE_INT_RGB); // 得到画笔对象             Graphics2D g = buffImg.createGraphics(); // 设置对线段的锯齿状边缘处理             g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,                     RenderingHints.VALUE_INTERPOLATION_BILINEAR);              g.drawImage(                     srcImg.getScaledInstance(srcImg.getWidth(null),                             srcImg.getHeight(null), Image.SCALE_SMOOTH), 0, 0,                     null); // 设置水印旋转角度（默认对角线角度） if (null != degree) {                 g.rotate(Math.toRadians(degree), (double) buffImg.getWidth() / 2, (double) buffImg.getHeight() / 2); } else { //根据三角形相关定理，计算对角线角度 double lengthOfDiagonal = Math.sqrt(buffImg.getWidth() * buffImg.getWidth() + buffImg.getHeight() * buffImg.getHeight()); double v = (Math.pow(buffImg.getWidth(), 2) + Math.pow(lengthOfDiagonal, 2) - Math.pow(buffImg.getHeight(), 2)) / (2 * buffImg.getWidth() * lengthOfDiagonal); double acos = Math.acos(v); double myDegree = Math.toDegrees(acos);                 g.rotate(-Math.toRadians(myDegree), (double) buffImg.getWidth() / 2, (double) buffImg.getHeight() / 2); } // 水印图片的路径 水印图片一般为gif或者png的，这样可设置透明度             ImageIcon imgIcon = new ImageIcon(iconPath);             Image img = imgIcon.getImage();             g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_ATOP,                     alpha)); // 水印图片的位置 int x = 0, y = 0; if (StringUtils.equals(location, "left-top")) {                 x = 30;                 y = 30; } else if (StringUtils.equals(location, "right-top")) {                 x = buffImg.getWidth() - img.getWidth(null) - 30;                 y = 30; } else if (StringUtils.equals(location, "left-bottom")) {                 x += 30;                 y = buffImg.getHeight() - img.getHeight(null) - 30; } else if (StringUtils.equals(location, "right-bottom")) {                 x = buffImg.getWidth() - img.getWidth(null) - 30;                 y = buffImg.getHeight() - img.getHeight(null) - 30; } else {                 x = (buffImg.getWidth() - img.getWidth(null)) / 2;                 y = (buffImg.getHeight() - img.getHeight(null)) / 2; }             g.drawImage(img, x, y, null);             g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER));             g.dispose(); // os = new FileOutputStream(targerPath);             os = response.getOutputStream();             ImageIO.write(buffImg, "JPG", os); } catch (Exception e) {             e.printStackTrace(); } finally { try { if (null != os)                     os.close(); } catch (Exception e) {                 e.printStackTrace(); } } } 

smbfile时也可以写成这样：

// 展示时 添加水印 public void showRemarkImage(String filePath, String iconPath, HttpServletRequest request, HttpServletResponse response) {   InputStream is = null;   OutputStream os = null;   ByteArrayOutputStream out = new ByteArrayOutputStream(); try {    SmbFile smbFile = new SmbFile(filePath);    is = smbFile.getInputStream();    os = response.getOutputStream();        Image srcImg = ImageIO.read(is);             BufferedImage buffImg = new BufferedImage(srcImg.getWidth(null),                     srcImg.getHeight(null), BufferedImage.TYPE_INT_RGB); // 得到画笔对象             Graphics2D g = buffImg.createGraphics(); // 设置对线段的锯齿状边缘处理             g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,                     RenderingHints.VALUE_INTERPOLATION_BILINEAR);              g.drawImage(srcImg.getScaledInstance(srcImg.getWidth(null), srcImg.getHeight(null), Image.SCALE_SMOOTH), 0, 0, null); // 旋转角度处理（根据三角形相关定理，计算对角线角度） //            double lengthOfDiagonal = Math.sqrt(buffImg.getWidth() * buffImg.getWidth() + buffImg.getHeight() * buffImg.getHeight()); //            double v = (Math.pow(buffImg.getWidth(), 2) + Math.pow(lengthOfDiagonal, 2) - Math.pow(buffImg.getHeight(), 2)) / (2 * buffImg.getWidth() * lengthOfDiagonal); //            double acos = Math.acos(v); //            double myDegree = Math.toDegrees(acos); //            g.rotate(-Math.toRadians(myDegree), (double) buffImg.getWidth() / 2, (double) buffImg.getHeight() / 2);             // 水印图片的路径 水印图片一般为gif或者png的，这样可设置透明度             ImageIcon imgIcon = new ImageIcon(iconPath);             Image img = imgIcon.getImage();             g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_ATOP, alpha)); // 水印图片居中 int x = 0, y = 0;                    x = (buffImg.getWidth() - img.getWidth(null)) / 2;             y = (buffImg.getHeight() - img.getHeight(null)) / 2;                       g.drawImage(img, x, y, null);             g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER));             g.dispose();                                  ImageIO.write(buffImg, "png", out); byte[] b = out.toByteArray();    response.addHeader("Content-Length", String.valueOf(b.length));            os.write(b, 0, b.length);    os.flush(); } catch (Exception e) {    LogUtil.error("附件下载失败，时间：" + DateUtil.formatToDateTimeText(new Date()) + "原因：" + e.getMessage()); //   throw new ApplicationException("文件读取失败：" + e.getMessage(), e); } finally {    IOUtils.closeQuietly(is);    IOUtils.closeQuietly(os);    IOUtils.closeQuietly(out); } }