我遇到过很多使用 PDFBox Layer Utility 的 appendFormAsLayer 方法的示例，如下所示:

 /**
 * Places the given form over the existing content of the indicated page (like an overlay).
 * The form is enveloped in a marked content section to indicate that it's part of an
 * optional content group (OCG), here used as a layer. This optional group is returned and
 * can be enabled and disabled through methods on {@link PDOptionalContentProperties}.
 * @param targetPage the target page
 * @param form the form to place
 * @param transform the transformation matrix that controls the placement
 * @param layerName the name for the layer/OCG to produce
 * @return the optional content group that was generated for the form usage
 * @throws IOException if an I/O error occurs
 */
public PDOptionalContentGroup appendFormAsLayer(PDPage targetPage,
        PDXObjectForm form, AffineTransform transform,
        String layerName) throws IOException
{
    PDDocumentCatalog catalog = targetDoc.getDocumentCatalog();
    PDOptionalContentProperties ocprops = catalog.getOCProperties();
    if (ocprops == null)
    {
        ocprops = new PDOptionalContentProperties();
        catalog.setOCProperties(ocprops);
    }
    if (ocprops.hasGroup(layerName))
    {
        throw new IllegalArgumentException("Optional group (layer) already exists: " + layerName);
    }

    PDOptionalContentGroup layer = new PDOptionalContentGroup(layerName);
    ocprops.addGroup(layer);

    PDResources resources = targetPage.findResources();
    PDPropertyList props = resources.getProperties();
    if (props == null)
    {
        props = new PDPropertyList();
        resources.setProperties(props);
    }

    //Find first free resource name with the pattern "MC<index>"
    int index = 0;
    PDOptionalContentGroup ocg;
    COSName resourceName;
    do
    {
        resourceName = COSName.getPDFName("MC" + index);
        ocg = props.getOptionalContentGroup(resourceName);
        index++;
    } while (ocg != null);
    //Put mapping for our new layer/OCG
    props.putMapping(resourceName, layer);

    PDPageContentStream contentStream = new PDPageContentStream(
            targetDoc, targetPage, true, !DEBUG);
    contentStream.beginMarkedContentSequence(COSName.OC, resourceName);
    contentStream.drawXObject(form, transform);
    contentStream.endMarkedContentSequence();
    contentStream.close();

    return layer;
}

前面代码中getPDFName调用中“MC”的意义是什么？

我编写了以下代码，在现有 pdf 的每一页上插入水印，并启用每组可选内容。

    LayerUtility layerUtility = new LayerUtility(document);
    PDXObjectForm form = layerUtility.importPageAsForm(overlayDoc, 0);
    for (int i = 0; i < document.getDocumentCatalog().getAllPages().size(); i++) {
        PDPage page = (PDPage) document.getDocumentCatalog().getAllPages().get(i);
        PDOptionalContentGroup ocGroup = layerUtility.appendFormAsLayer(page, form, new AffineTransform(), "watermark" + i);
    }



    PDOptionalContentProperties ocprops = document.getDocumentCatalog().getOCProperties();

    for (String groupName : ocprops.getGroupNames()) {
        if (groupName.startsWith("watermark")) {
            ocprops.setGroupEnabled(groupName, true);
        }
    }

将组设置为启用或禁用“setGroupEnabled(groupName, true)”会导致它在显示和打印时显示。根据我研究过的有关此主题的其他信息，可以在可选内容可见时进行更精细的调整，这表明存在 onScreen 和 onPrint boolean 属性，可以设置这些属性以确定内容的可见性。参见 https://acrobatusers.com/tutorials/watermarking-a-pdf-with-javascript

有没有办法使用 PDFBox 使水印在打印时可见但在显示时不可见？如果没有，我们将不胜感激任何替代解决方案的建议。

这里是从字符串 (createOverlay) 和调用 LayerUtility 传递水印文档的函数 (addWatermark) 创建水印 pdf 的附加代码。所需要做的就是从任何现有的 pdf 文件创建一个 PDDocument 并将其与水印字符串一起传递。

public PDDocument addWatermark(PDDocument document, String text) throws IOException {
    PDDocument overlayDoc = createOverlay(text);
    //  Create the watermark in an optional content group
    LayerUtility layerUtility = new LayerUtility(document);
    PDXObjectForm form = layerUtility.importPageAsForm(overlayDoc, 0);
    for (int i = 0; i < document.getDocumentCatalog().getAllPages().size(); i++) {
        PDPage page = (PDPage) document.getDocumentCatalog().getAllPages().get(i);
        layerUtility.appendFormAsLayer(page, form, new AffineTransform(), "watermark" + i);
    }
    return document;        
}

private PDDocument createOverlay(String text) throws IOException {
    // Create a document and add a page to it
    PDDocument document = new PDDocument();
    PDPage page = new PDPage();
    document.addPage(page);

    PDExtendedGraphicsState extendedGraphicsState = new PDExtendedGraphicsState();
     // Set the transparency/opacity
     extendedGraphicsState.setNonStrokingAlphaConstant(0.4f);
     if (page.findResources() == null) {
         page.setResources(new PDResources());
     }
     PDResources resources = page.findResources();// Get the page resources.
     // Get the defined graphic states.
     if (resources.getGraphicsStates() == null)
     {
         resources.setGraphicsStates(new HashMap<String, PDExtendedGraphicsState>());
     }
     Map<String, PDExtendedGraphicsState> graphicsStateDictionary = resources.getGraphicsStates();

      if (graphicsStateDictionary != null){ 
          graphicsStateDictionary.put("TransparentState", extendedGraphicsState); 
          resources.setGraphicsStates(graphicsStateDictionary); 
     }

    // the x/y coords
    Float xVal = 0f; //Float.parseFloat(config.getProperty("ss.xVal"));
    Float yVal = 0f; //Float.parseFloat(config.getProperty("ss.yVal"));

    // Start a new content stream which will "hold" the to be created content
    PDPageContentStream contentStream = new PDPageContentStream(document, page, true, true);
      contentStream.appendRawCommands("/TransparentState gs\n");

    // Create the text and position it
    contentStream.beginText();
    contentStream.setFont(font, fontSize);
    contentStream.setTextRotation(Math.PI/4,page.getMediaBox().getWidth()/4,page.getMediaBox().getHeight()/4);
    contentStream.setNonStrokingColor(210,210,210); //light grey
    contentStream.moveTextPositionByAmount(xVal, yVal);
    contentStream.drawString(text);
    contentStream.endText();

    // Make sure that the content stream is closed:
    contentStream.close();

    //return the string doc
    return document;
}

最佳答案

private void addWaterMark(PDDocument document) throws Exception
{
    PDDocumentCatalog catalog = document.getDocumentCatalog();
    PDOptionalContentProperties ocprops = catalog.getOCProperties();
    if (ocprops == null)
    {
        ocprops = new PDOptionalContentProperties();
        ocprops.setBaseState(BaseState.OFF);
        catalog.setOCProperties(ocprops);
    }
    String layerName = "conWatermark";
    PDOptionalContentGroup watermark = null;
    if (ocprops.hasGroup(layerName))
    {
        watermark = ocprops.getGroup(layerName);
    }
    else
    {
        watermark = new PDOptionalContentGroup(layerName);
        ocprops.addGroup(watermark);
    }

    COSDictionary watermarkDic = watermark.getCOSObject();
    COSDictionary printState = new COSDictionary();
    printState.setItem("PrintState", COSName.ON);
    COSDictionary print = new COSDictionary();
    print.setItem("Print", printState);
    watermarkDic.setItem("Usage", print);

    COSDictionary asPrint = new COSDictionary();
    asPrint.setItem("Event", COSName.getPDFName("Print"));
    COSArray category = new COSArray();
    category.add(COSName.getPDFName("Print"));
    asPrint.setItem("Category", category);
    COSArray ocgs = new COSArray();
    ocgs.add(watermarkDic);
    asPrint.setItem(COSName.OCGS, ocgs);
    COSArray as = new COSArray();
    as.add(asPrint);
    COSDictionary d = (COSDictionary) ((COSDictionary) ocprops.getCOSObject()).getDictionaryObject(COSName.D);
    d.setItem(COSName.AS, as);

    for (int n = 0; n < document.getNumberOfPages(); n++)
    {
        PDPage page = document.getPage(n);

        PDResources resources = page.getResources();
        if (resources == null)
        {
            resources = new PDResources();
            page.setResources(resources);
        }

        String text1 = "Confidential";
        String text2 = "Document ..."; //

        PDExtendedGraphicsState graphicsState = new PDExtendedGraphicsState();
        graphicsState.setNonStrokingAlphaConstant(0.08f);

        PDPageContentStream contentStream = new PDPageContentStream(document, page, AppendMode.APPEND, true, true);
        contentStream.setGraphicsStateParameters(graphicsState);
        contentStream.setNonStrokingColor(Color.GRAY);

        contentStream.beginMarkedContent(COSName.OC, watermark);

        contentStream.beginText();

        PDRectangle pageSize = page.getBBox();
        float fontSize = this.getFittingFontSize(pageSize, text1);
        PDFont font = this.WATERMARK_FONT;
        contentStream.setFont(font, fontSize);
        float text1Width = this.getTextWidth(font, fontSize, text1);
        float rotation = (float) Math.atan(pageSize.getHeight() / pageSize.getWidth());
        Point p = this.getStartPoint(pageSize, fontSize, text1);
        AffineTransform at = new AffineTransform(1, 0, 0, 1, p.getX(), p.getY());
        at.rotate(rotation);
        Matrix matrix = new Matrix(at);
        contentStream.setTextMatrix(matrix);
        contentStream.showText(text1);

        fontSize = this.getFittingFontSize(pageSize, text2);
        contentStream.setFont(font, fontSize);
        contentStream.newLineAtOffset(-(this.getTextWidth(font, fontSize, text2) - text1Width) / 2, -fontSize * 1.2f);
        contentStream.showText(text2);
        contentStream.endMarkedContent();
        contentStream.endText();
        contentStream.close();
    }
}

关于java - 创建仅在使用 PDFBox 打印时显示的水印(pdf 可选内容)，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/31683515/