c#itextsharp PDF创建,每页带水印 [英] c# itextsharp PDF creation with watermark on each page
问题描述
我正在尝试使用 itextsharp(Java 的 itext 的 C# 端口)以编程方式创建许多带有水印的 PDF 文档.
I am trying to programmatically create a number of PDF documents with a watermark on each page using itextsharp (a C# port of Java's itext).
在使用 PdfStamper 创建文档后,我可以执行此操作.然而,这似乎涉及重新打开文档阅读它,然后在每页上创建一个带有水印的新文档.
I am able to do this after the document has been created using a PdfStamper. However this seems to involve re-opening the document reading it and then creating a new document with the watermark on each page.
有没有办法在文档创建过程中做到这一点?
Is there a way of doing this during document creation?
推荐答案
深入研究后,我发现最好的方法是在每个页面创建时为其添加水印.为此,我创建了一个新类并实现了 IPdfPageEvent 接口,如下所示:
After digging into it I found the best way was to add the watermark to each page as it was created. To do this I created a new class and implemented the IPdfPageEvent interface as follows:
class PdfWriterEvents : IPdfPageEvent
{
string watermarkText = string.Empty;
public PdfWriterEvents(string watermark)
{
watermarkText = watermark;
}
public void OnOpenDocument(PdfWriter writer, Document document) { }
public void OnCloseDocument(PdfWriter writer, Document document) { }
public void OnStartPage(PdfWriter writer, Document document) {
float fontSize = 80;
float xPosition = 300;
float yPosition = 400;
float angle = 45;
try
{
PdfContentByte under = writer.DirectContentUnder;
BaseFont baseFont = BaseFont.CreateFont(BaseFont.HELVETICA, BaseFont.WINANSI, BaseFont.EMBEDDED);
under.BeginText();
under.SetColorFill(BaseColor.LIGHT_GRAY);
under.SetFontAndSize(baseFont, fontSize);
under.ShowTextAligned(PdfContentByte.ALIGN_CENTER, watermarkText, xPosition, yPosition, angle);
under.EndText();
}
catch (Exception ex)
{
Console.Error.WriteLine(ex.Message);
}
}
public void OnEndPage(PdfWriter writer, Document document) { }
public void OnParagraph(PdfWriter writer, Document document, float paragraphPosition) { }
public void OnParagraphEnd(PdfWriter writer, Document document, float paragraphPosition) { }
public void OnChapter(PdfWriter writer, Document document, float paragraphPosition, Paragraph title) { }
public void OnChapterEnd(PdfWriter writer, Document document, float paragraphPosition) { }
public void OnSection(PdfWriter writer, Document document, float paragraphPosition, int depth, Paragraph title) { }
public void OnSectionEnd(PdfWriter writer, Document document, float paragraphPosition) { }
public void OnGenericTag(PdfWriter writer, Document document, Rectangle rect, String text) { }
}
}
这个对象被注册来处理如下事件:
This object is registered to handle the events as follows:
PdfWriter docWriter = PdfWriter.GetInstance(document, new FileStream(outputLocation, FileMode.Create));
PdfWriterEvents writerEvent = new PdfWriterEvents(watermark);
docWriter.PageEvent = writerEvent;
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