保护 PDF

Question

我目前正在使用Apache FOP 库来生成 PDF。我希望保护这些 PDF 免受复制粘贴，因此人们必须使用实际的 OCR 库（或手动输入）来获取 PDF 上的信息。

FOP 显然提供了一些安全性，然后将其添加为 PDF 上的meta-data，以防止打印或复制等事情，但这似乎无法正常工作（打印时无法禁用复制粘贴已启用等）。

对我来说似乎直截了当的一种可能性基本上是以某种方式将 PDF 上的所有文本转换为图像，但我找不到有关此事的任何信息。

显然，我不在乎 PDF 是否可搜索。我只是想防止人们在他们仍然可以打印的时候复制粘贴。

我当前的 FOP 代码：

private static FopFactory fopFactory;

private static FopFactory initializeFactory() throws IOException,
        SAXException {
    if (fopFactory == null) {
        File f = new File(SettingUtil.getSetting(LetterGeneratorSettings.FOP_CONFIG_LOCATION));
        fopFactory = FopFactory.newInstance(f);
    }
    return fopFactory;
}

public static File generatePDFFromXML(File fopTemplate, File xmlSource,
        File resultFileLocation) throws IOException {
    try {
        initializeFactory();
        URL url = fopTemplate.toURI().toURL();
        // creation of transform source
        StreamSource transformSource = new StreamSource(url.openStream());
        // create an instance of fop factory

        // a user agent is needed for transformation
        FOUserAgent foUserAgent = fopFactory.newFOUserAgent();
        foUserAgent.getRendererOptions().put("encryption-params",
                getEncryptionParams());
        // to store output
        ByteArrayOutputStream pdfoutStream = new ByteArrayOutputStream();
        StreamSource source = new StreamSource(new ByteArrayInputStream(IOUtils.toByteArray(new FileInputStream(xmlSource))));
        Transformer xslfoTransformer;
        try {
            TransformerFactory transfact = TransformerFactory.newInstance();

            xslfoTransformer = transfact.newTransformer(transformSource);
            // Construct fop with desired output format
            Fop fop;
            try {
                fop = fopFactory.newFop(MimeConstants.MIME_PDF, foUserAgent, pdfoutStream);
                // Resulting SAX events (the generated FO)
                // must be piped through to FOP
                Result res = new SAXResult(fop.getDefaultHandler());

                // Start XSLT transformation and FOP processing
                try {
                    // everything will happen here..
                    xslfoTransformer.transform(source, res);

                    // if you want to save PDF file use the following code
                    OutputStream out = new java.io.FileOutputStream(resultFileLocation);
                    out = new java.io.BufferedOutputStream(out);
                    FileOutputStream str = new FileOutputStream(resultFileLocation);
                    str.write(pdfoutStream.toByteArray());
                    str.close();
                    out.close();

                } catch (TransformerException e) {
                    e.printStackTrace();
                }
            } catch (FOPException e) {
                e.printStackTrace();
            }
        } catch (TransformerConfigurationException e) {
            e.printStackTrace();
        } catch (TransformerFactoryConfigurationError e) {
            e.printStackTrace();
        }
        return resultFileLocation;
    } catch (Exception ex) {
        throw new IOException(ex);
    }
}

private static PDFEncryptionParams getEncryptionParams() {
    return new PDFEncryptionParams(null,
            SettingUtil.getSetting(LetterGeneratorSettings.PDF_PASSWORD),
            true, false, false, false, false);
}

以下是我的fopconfig.xml

的内容

    <fop version="1.0">

  <!-- Strict user configuration -->
  <strict-configuration>false</strict-configuration>

  <!-- Strict FO validation -->
  <strict-validation>false</strict-validation>

  <!-- Base URL for resolving relative URLs -->
  <base>./</base>

  <!-- Font Base URL for resolving relative font URLs -->
  <font-base>./</font-base>

  <!-- Source resolution in dpi (dots/pixels per inch) for determining the size of pixels in SVG and bitmap images, default: 72dpi -->
  <source-resolution>72</source-resolution>
  <!-- Target resolution in dpi (dots/pixels per inch) for specifying the target resolution for generated bitmaps, default: 72dpi -->
  <target-resolution>72</target-resolution>

  <!-- default page-height and page-width, in case
       value is specified as auto -->
  <default-page-settings height="11in" width="8.26in"/>

  <!-- etc. etc..... -->
</fop>

Answer 1

我不确定它如何与 Apache FOP 一起使用，但使用 iText lib 很容易。

这是我不久前写的关于这个http://tutors4all.net/index.php/2015/05/06/encrypt-pdf-file/的教程