iText：如何在同一文档中插入背景图像以刷新响应 [英] iText : How do I insert background image in the same document to be flushed to response

问题描述

我正在创建PDF并编写流作为响应。在写入流之前，我想在所有页面中添加背景图像作为水印，以便通过响应刷新的PDF文档是带有水印的最终文档。

I am creating a PDF and writing the stream in response. Before writing in the stream, I want to add a background image as watermark in all the pages so that PDF document flushed through response is the final one with watermark.

嗨这个是我的代码示例。任何帮助都会得到很多帮助

Hi this is my code sample. Any help would be much appriciated

private static String generatePDF(HttpServletRequest request, HttpServletResponse   response, String fileName) throws Exception
{
    Document document = null;
    PdfWriter writer = null;
    FileOutputStream fos = null;
    try
    {
       fos = new FileOutputStream(fileName);
       Document document = new Document(PageSize.A4);
       writer = PdfWriter.getInstance(document, fos);
       document.open();

       /**
        * Adding tables and cells and other stuff required
        **/

       return pdfFileName;
  } catch (Exception e) {
       FileUtil.deleteFile(fileName);
       throw e
  } finally {
    if (document != null) {
        document.close();
    }
    fos.flush();
  }
}

我现在想要添加背景图片下面的代码并将输出PDF写入同一个流

I now would like to add a background image using the below code and write the output PDF to the same stream

PdfReader sourcePDFReader = null;
try
{
   sourcePDFReader = new PdfReader(sourcePdfFileName);
   int noOfPages = sourcePDFReader.getNumberOfPages();
   PdfStamper stamp = new PdfStamper(sourcePDFReader, new FileOutputStream(destPdfFileName));
   int i = 0;
   Image templateImage = Image.getInstance(templateImageFile);
   templateImage.setAbsolutePosition(0, 0);
   PdfContentByte tempalteBytes;
   while (i < noOfPages) {
       i++;
       tempalteBytes = stamp.getUnderContent(i);
       tempalteBytes.addImage(templateImage);
   }
   stamp.close();
   return destPdfFileName;
} catch (Exception ex) {
   LOGGER.log(Level.INFO, "Error when applying tempalte image as watermark");
} finally {
     if (sourcePDFReader != null) {
         sourcePDFReader.close();
     }
}

推荐答案

我使用Bruno的第一个（推荐）方法解决了这个问题。

I solved this using Bruno's first (recommended) approach.

1）使用 onEndPage 事件创建一个页面事件助手：

1) Create a page event helper with an onEndPage event:

class PDFBackground extends PdfPageEventHelper {

    @Override
    void onEndPage(PdfWriter writer, Document document) {
        Image background = Image.getInstance("myimage.png");
        // This scales the image to the page,
        // use the image's width & height if you don't want to scale.
        float width = document.getPageSize().getWidth();
        float height = document.getPageSize().getHeight();
        writer.getDirectContentUnder()
                .addImage(background, width, 0, 0, height, 0, 0);
    }

}

2）创建作家时，注册您的页面事件助手：

2) When creating your writer, register your page event helper:

PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(file));
writer.setPageEvent(new PDFBackground());

这篇关于iText：如何在同一文档中插入背景图像以刷新响应的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！