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);
}
}
