Pdf添加水印功能
背景
为防止涉密文件泄露，用户预览或下载pdf文件时，需要以用户信息作为水印内容加到pdf文件中。
实现
附件下载/预览接口：
/// <summary>
/// pdf附件下载接口
/// </summary>
/// <param name="fileId">fileId</param>
/// <param name="userId">用户id</param>
/// <returns></returns>
[HttpGet("{fileId}/{userId}")]
[AllowAnonymous]
public IActionResult DownloadPdfFile(string fileId,string userId)
{
//从Mongo中下载文件
FileByteInfo file = this._fileService.DownloadFileStream(fileId);
if (file == null) return Ok("文件不存在或已被删除!");
string type = "";
System.IO.Stream fileStream = file.FileStream; //文件流
string fileName = file.FileName;
if (!string.IsNullOrWhiteSpace(userId))
{
//获取用户身份
User user = this._userService.GetUser(userId);
if (user != null)
{
//水印：姓名(登录名 所属部门)
string waterMarkText = $"{user.Name}({user.Code}) {user.ParentName}";
System.IO.Stream waterPdfStream = PDFHelper.AddWatermark(fileStream, waterMarkText);
//pdf添加水印
if (waterPdfStream != null)
{
fileStream = waterPdfStream;
}
}
}
System.IO.Stream fbyte = fileStream;
try
{
var provider = new FileExtensionContentTypeProvider();
type = provider.Mappings[file.ContentType];
}
catch (KeyNotFoundException)
{
type = "application/x-msdownload";
}
return File(fbyte, type, fileName);
}
● 根据file获取文件流，调用AddWatermark将流添加水印
PDFHelper类：
若出现本地调试支持，部署到docker后预览出错，可能是服务器字体问题：
//本地调用这个配置
BaseFont font = BaseFont.CreateFont("STSong-Light", "UniGB-UCS2-H", BaseFont.NOT_EMBEDDED);
//docker下用这个配置
BaseFont font = BaseFont.CreateFont("/usr/share/fonts/simhei.ttf", BaseFont.IDENTITY_H, BaseFont.NOT_EMBEDDED);
public static class PDFHelper
{
/// <summary>
/// 添加倾斜水印
/// </summary>
/// <param name="pdfStream">pdf文件流</param>
/// <param name="waterMarkName">水印字符串</param>
/// <param name="width">页面宽度</param>
/// <param name="height">页面高度</param>
public static MemoryStream AddWatermark(Stream pdfStream, string waterMarkName)
{
PdfReader pdfReader = null;
PdfStamper pdfStamper = null;
MemoryStream outStream = new MemoryStream();
try
{
pdfStream.Position = 0;
pdfReader = new PdfReader(pdfStream);
pdfStamper = new PdfStamper(pdfReader, outStream);
int total = pdfReader.NumberOfPages + 1;
iTextSharp.text.Rectangle psize = pdfReader.GetPageSize(1);
float width = psize.Width;
float height = psize.Height;
PdfContentByte content;
//本地调用这个配置
//BaseFont font = BaseFont.CreateFont("STSong-Light", "UniGB-UCS2-H", BaseFont.NOT_EMBEDDED);
//docker下用这个配置
BaseFont font = BaseFont.CreateFont("/usr/share/fonts/simhei.ttf", BaseFont.IDENTITY_H, BaseFont.NOT_EMBEDDED);
PdfGState gs = new PdfGState();
int fontSize = 28;
for (int i = 1; i < total; i++)
{
//在内容上方加水印 ;content = pdfStamper.GetUnderContent(i);//在内容下方加水印
content = pdfStamper.GetOverContent(i);
gs.FillOpacity = 0.5f; //透明度
content.SetGState(gs);
content.SetGrayFill(0.5f);
//开始写入文本
content.BeginText();
content.SetColorFill(BaseColor.Blue);
content.SetFontAndSize(font, fontSize);
content.ShowTextAligned(Element.ALIGN_CENTER, waterMarkName, width / 2 + 150, height / 2 + 150, 55);
content.SetColorFill(BaseColor.Blue);
content.SetFontAndSize(font, fontSize);
content.ShowTextAligned(Element.ALIGN_CENTER, waterMarkName, width / 2 - 150, height / 2 - 150, 55);
content.EndText();
}
}
catch (Exception ex)
{
Console.WriteLine($"AddWatermark error:{ex.Message}, innerException:{ex.InnerException?.Message},stack:{ex.StackTrace}");
outStream = null;
}
finally
{
if (pdfStamper != null)
pdfStamper.Close();
if (pdfReader != null)
pdfReader.Close();
if (outStream != null)
outStream.Position = 0; //必须重置位置，再写MongoDB
}
return outStream;
}
/// <summary>
/// 加图片水印
/// </summary>
/// <param name="inputfilepath">源文件路径</param>
/// <param name="outputfilepath">输出路径</param>
/// <param name="modelPicName">图片地址</param>
/// <param name="top">图片水印top</param>
/// <param name="left">图片水印left</param>
/// <returns></returns>
public static bool AddImageWatermarkPDF(string inputfilepath, string outputfilepath, string modelPicName, float top, float left)
{
PdfReader pdfReader = null;
PdfStamper pdfStamper = null;
try
{
pdfReader = new PdfReader(inputfilepath);
int numberOfPages = pdfReader.NumberOfPages;
iTextSharp.text.Rectangle psize = pdfReader.GetPageSize(1);
float width = psize.Width;
float height = psize.Height;
pdfStamper = new PdfStamper(pdfReader, new FileStream(outputfilepath, FileMode.Create));
PdfContentByte waterMarkContent;
iTextSharp.text.Image image = iTextSharp.text.Image.GetInstance(modelPicName);
image.GrayFill = 20;//透明度，灰色填充
//image.Rotation //旋转
//image.RotationDegrees //旋转角度
//水印的位置
if (left < 0)
{
left = width / 2 - image.Width + left;
}
//image.SetAbsolutePosition(left, (height - image.Height) - top);
image.SetAbsolutePosition(left, (height / 2 - image.Height) - top);
//每一页加水印,也可以设置某一页加水印
for (int i = 1; i <= numberOfPages; i++)
{
//waterMarkContent = pdfStamper.GetUnderContent(i);//内容下层加水印
waterMarkContent = pdfStamper.GetOverContent(i);//内容上层加水印
waterMarkContent.AddImage(image);
}
return true;
}
catch (Exception ex)
{
throw ex;
}
finally
{
if (pdfStamper != null)
pdfStamper.Close();
if (pdfReader != null)
pdfReader.Close();
}
}
/// <summary>
/// 添加普通偏转角度文字水印
/// </summary>
/// <param name="inputfilepath">源文件路径</param>
/// <param name="outputfilepath">输出路径</param>
/// <param name="waterMarkName">水印内容</param>
public static void AddWordWatermark2PDF(string inputfilepath, string outputfilepath, string waterMarkName)
{
//PDFHelper.AddWordWatermark2PDF("F:\\pdf1.pdf", "F:\\pdf1副本.pdf", "我是水印内容");
PdfReader pdfReader = null;
PdfStamper pdfStamper = null;
try
{
pdfReader = new PdfReader(inputfilepath);
pdfStamper = new PdfStamper(pdfReader, new FileStream(outputfilepath, FileMode.Create));
int total = pdfReader.NumberOfPages + 1;
iTextSharp.text.Rectangle psize = pdfReader.GetPageSize(1);
float width = psize.Width;
float height = psize.Height;
PdfContentByte content;
BaseFont font = BaseFont.CreateFont(@"C:\WINDOWS\Fonts\SIMFANG.TTF", BaseFont.IDENTITY_H, BaseFont.EMBEDDED);
PdfGState gs = new PdfGState();
for (int i = 1; i < total; i++)
{
//在内容上方加水印
content = pdfStamper.GetUnderContent(i);
//content = pdfStamper.GetUnderContent(i);//在内容下方加水印
//透明度
gs.FillOpacity = 0.5f;
content.SetGState(gs);
content.SetGrayFill(0.5f);
//开始写入文本
content.BeginText();
//content.SetColorFill(BaseColor.LIGHT_GRAY);
//content.SetFontAndSize(font, 100);
//content.SetTextMatrix(0, 0);
//content.ShowTextAligned(Element.ALIGN_CENTER, waterMarkName, width / 2 - 50, height / 2 - 50, 55);
content.SetColorFill(BaseColor.Gray);
content.SetFontAndSize(font, 16);
content.ShowTextAligned(Element.ALIGN_CENTER, waterMarkName, width / 2 - 50, height / 2 - 50, 55);
content.EndText();
}
}
catch (Exception ex)
{
throw ex;
}
finally
{
if (pdfStamper != null)
pdfStamper.Close();
if (pdfReader != null)
pdfReader.Close();
}
}
}
效果图
