iText - 向现有PDF文件添加内容 [英] iText - add content to existing PDF file

问题描述

我想用iText执行以下操作：

I want to do the following with iText:

（1）解析现有PDF文件

(1) parse an existing PDF file

（2）在文档的现有单页上添加一些数据（如时间戳）

(2) add some data to it, on the existing single page of the document (such as a timestamp)

（3）写出文档

我似乎无法弄清楚如何使用iText做到这一点。在伪代码中，我会这样做：

I just can't seem to figure out how to do this with iText. In pseudo code I would do this:

Document document = reader.read(input);
document.add(new Paragraph("my timestamp"));
writer.write(document, output);

但由于某种原因，iText的API非常复杂，我无法理解它。 PdfReader实际上保存文档模型或其他东西（而不是吐出文档），你需要一个PdfWriter来读取它的页面...呃？

But for some reason iText's API is so dauntingly complicated that I can't wrap my head around it. The PdfReader actually holds the document model or something (rather than spitting out a document), and you need a PdfWriter to read pages from it... eh?

推荐答案

iText有多种方法可以做到这一点。 PdfStamper 类是一个选项。但我发现最简单的方法是创建一个新的PDF文档，然后将现有文档中的各个页面导入到新的PDF中。

iText has more than one way of doing this. The PdfStamper class is one option. But I find the easiest method is to create a new PDF document then import individual pages from the existing document into the new PDF.

// Create output PDF
Document document = new Document(PageSize.A4);
PdfWriter writer = PdfWriter.getInstance(document, outputStream);
document.open();
PdfContentByte cb = writer.getDirectContent();

// Load existing PDF
PdfReader reader = new PdfReader(templateInputStream);
PdfImportedPage page = writer.getImportedPage(reader, 1); 

// Copy first page of existing PDF into output PDF
document.newPage();
cb.addTemplate(page, 0, 0);

// Add your new data / text here
// for example...
document.add(new Paragraph("my timestamp")); 

document.close();

这将从 templateInputStream中读取PDF 并写出 outputStream 。这些可能是文件流或内存流或任何适合您应用程序的内容。

This will read in a PDF from templateInputStream and write it out to outputStream. These might be file streams or memory streams or whatever suits your application.

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