C#使用iTextSharp给PDF添加水印

/// <summary>
/// 添加普通偏转角度文字水印
/// </summary>
public static void SetWatermark(string filePath, string text)
{
PdfReader pdfReader = null;
PdfStamper pdfStamper = null;
string tempPath = Path.GetDirectoryName(filePath) + Path.GetFileNameWithoutExtension(filePath) + "_temp.pdf";

try
{
pdfReader = new PdfReader(filePath);
pdfStamper = new PdfStamper(pdfReader, new FileStream(tempPath, 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++)
{
content = pdfStamper.GetOverContent(i);//在内容上方加水印
//content = pdfStamper.GetUnderContent(i);//在内容下方加水印
//透明度
gs.FillOpacity = 0.3f;
content.SetGState(gs);
//content.SetGrayFill(0.3f);
//开始写入文本
content.BeginText();
content.SetColorFill(BaseColor.GRAY);
content.SetFontAndSize(font, 30);
content.SetTextMatrix(0, 0);
content.ShowTextAligned(Element.ALIGN_CENTER, text, width - 120, height - 120, -45);
//content.SetColorFill(BaseColor.BLACK);
//content.SetFontAndSize(font, 8);
//content.ShowTextAligned(Element.ALIGN_CENTER, waterMarkName, 0, 0, 0);
content.EndText();
}
}
catch (Exception ex)
{
throw ex;
}
finally
{
if (pdfStamper != null)
pdfStamper.Close();

if (pdfReader != null)
pdfReader.Close();
System.IO.File.Copy(tempPath, filePath, true);
System.IO.File.Delete(tempPath);
}
}