java如何给图片加水印？
这篇文章给大家分享的是java给图片加水印的方法，相信大部分人都还没学会这个技能，为了让大家更加了解，给大家总结了以下内容，话不多说，一起往下看吧。
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具体代码：
// 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);
}
}以上就是java给图片加水印的方法，代码详细清楚，如果在日常工作遇到这个问题，希望你能通过这篇文章解决问题。如果想了解更多相关内容，欢迎关注创新互联行业资讯频道！
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