用PDFBox加水印

Question

我正在尝试使用PDFBox专门为PDF添加水印。我已经能够使图像显示在每个页面上，但是它失去了背景透明度，因为它看起来好像PDJpeg将其转换为JPG。也许有一种使用PDXObjectImage的方法。

到目前为止，这是我写的内容：

public static void watermarkPDF(PDDocument pdf) throws IOException
{
    // Load watermark
    BufferedImage buffered = ImageIO.read(new File("C:\\PDF_Test\\watermark.png"));
    PDJpeg watermark = new PDJpeg(pdf, buffered);

    // Loop through pages in PDF
    List pages = pdf.getDocumentCatalog().getAllPages();
    Iterator iter = pages.iterator();
    while(iter.hasNext())
    {
        PDPage page = (PDPage)iter.next();

        // Add watermark to individual page
        PDPageContentStream stream = new PDPageContentStream(pdf, page, true, false);
        stream.drawImage(watermark, 100, 0);
        stream.close();
    }

    try 
    {
        pdf.save("C:\\PDF_Test\\watermarktest.pdf");
    } 
    catch (COSVisitorException e) 
    {
        e.printStackTrace();
    }
}

Answer 1

更新的答案 （更好的版本，带有简单的水印方法，这要感谢下面的评论员和@okok的回答提供了输入）

如果您使用的是PDFBox
1.8.10或更高版本，则可以轻松地将水印添加到PDF文档中，从而更好地控制需要对哪些页面进行水印处理。假设您有一个包含水印图像的一页PDF文档，则可以按如下所示将此文档叠加在要加水印的文档上。

使用1.8.10的示例代码

import java.util.HashMap;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.util.Overlay;

public class TestPDF {
    public static void main(String[] args) throws Exception{
            PDDocument realDoc = PDDocument.load("originaldocument.pdf"); 
            //the above is the document you want to watermark

            //for all the pages, you can add overlay guide, indicating watermark the original pages with the watermark document.
            HashMap<Integer, String> overlayGuide = new HashMap<Integer, String>();
            for(int i=0; i<realDoc.getPageCount(); i++){
                overlayGuide.put(i+1, "watermark.pdf");
                //watermark.pdf is the document which is a one page PDF with your watermark image in it. Notice here that you can skip pages from being watermarked.
            }
            Overlay overlay = new Overlay();
            overlay.setInputPDF(realDoc);
            overlay.setOutputFile("final.pdf");
            overlay.setOverlayPosition(Overlay.Position.BACKGROUND);
            overlay.overlay(overlayGuide,false);
           //final.pdf will have the original PDF with watermarks.

使用PDFBox 2.0.0候选版本的示例

import java.io.File;
import java.util.HashMap;
import org.apache.pdfbox.multipdf.Overlay;
import org.apache.pdfbox.pdmodel.PDDocument;

public class TestPDF {

    public static void main(String[] args) throws Exception{        
        PDDocument realDoc = PDDocument.load(new File("originaldocument.pdf"));
        //the above is the document you want to watermark
        //for all the pages, you can add overlay guide, indicating watermark the original pages with the watermark document.

        HashMap<Integer, String> overlayGuide = new HashMap<Integer, String>();
        for(int i=0; i<realDoc.getNumberOfPages(); i++){
            overlayGuide.put(i+1, "watermark.pdf");
            //watermark.pdf is the document which is a one page PDF with your watermark image in it. 
            //Notice here, you can skip pages from being watermarked.
        }
        Overlay overlay = new Overlay();
        overlay.setInputPDF(realDoc);
        overlay.setOutputFile("final.pdf");
        overlay.setOverlayPosition(Overlay.Position.BACKGROUND);
        overlay.overlay(overlayGuide);      
    }
}

如果要将新的软件包org.apache.pdfbox.tools.OverlayPDF用于覆盖，则可以采用这种方法。（感谢下面的海报）

String[] overlayArgs = {"C:/Examples/foreground.pdf", "C:/Examples/background.pdf", "C:/Examples/resulting.pdf"};
OverlayPDF.main(overlayArgs);
System.out.println("Overlay finished.");

旧答案 低效方式，不建议使用。

好吧，OP问如何在PDFBox中做到这一点，第一个答案看起来像一个使用iText的示例。在PDFBox中创建水印非常简单。诀窍是，您应该具有带水印图像的空白PDF文档。然后，您要做的就是将此水印文档覆盖在要添加水印的文档上。

PDDocument watermarkDoc = PDDocument.load("watermark.pdf");
//Assuming your empty document with watermark image in it.

PDDocument realDoc = PDDocument.load("document-to-be-watermarked.pdf");
//Let's say this is your document that you want to watermark. For example sake, I am opening a new one, you would already have a reference to PDDocument if you are creating one

Overlay overlay = new Overlay();
overlay.overlay(realDoc,watermarkDoc);
watermarkDoc.save("document-now-watermarked.pdf");

警告：您应确保两个文档中的页数均匹配。否则，最终将得到一个文档，其页数与页数最少的文档相匹配。您可以操纵水印文档并复制页面以匹配您的文档。

希望这可以帮助。！