Java iText移动水印位置

如何解决Java iText移动水印位置

我有以下代码将图像缩放到A4大小：

  void scale(PdfDocument pdfDocument,Rectangle pageSize,Rectangle pageBodySize) {
    int n = pdfDocument.getNumberOfPages();

    for (int i = 1; i <= n; i++) {
        PdfPage page = pdfDocument.getPage(i);

        MarginFinder marginFinder = new MarginFinder();
        PdfCanvasProcessor pdfCanvasProcessor = new PdfCanvasProcessor(marginFinder);
        pdfCanvasProcessor.processPageContent(page);
        Rectangle boundingBox = marginFinder.getBoundingBox();
        if (boundingBox == null || boundingBox.getWidth() == 0 || boundingBox.getHeight() == 0) {
            LOG.warn("Cannot scale page %d contents with bounding box %s\n",i,boundingBox);
            continue;
        } else {
            // Scale and move content into A4 with margin
            double scale = 0,xDiff = 0,yDiff = 0;
            double xScale = pageBodySize.getWidth() / boundingBox.getWidth();
            double yScale = pageBodySize.getHeight() / boundingBox.getHeight();
            if (xScale < yScale) {
                yDiff = boundingBox.getHeight() * (yScale / xScale - 1) / 2;
                scale = xScale;
            } else {
                xDiff = boundingBox.getWidth() * (xScale / yScale - 1) / 2;
                scale = yScale;
            }

            AffineTransform transform = AffineTransform.getTranslateInstance(pageBodySize.getLeft() + xDiff,pageBodySize.getBottom() + yDiff);
            transform.scale(scale,scale);
            transform.translate(-boundingBox.getLeft(),-boundingBox.getBottom());

            new PdfCanvas(page.newContentStreamBefore(),page.getResources(),pdfDocument)
                    .concatMatrix(transform);

        }
        page.setMediaBox(pageSize);
        page.setCropBox(pageSize);
    }
}

此方法在这里调用：

 ByteArrayOutputStream mergedPdfStream = new ByteArrayOutputStream();
    PdfDocument mergedPdf = new PdfDocument(new PdfWriter(mergedPdfStream));

    for (PdfDocument doc : pdfDocuments) {
        int n = doc.getNumberOfPages();
       
        for (int i = 1; i <= n; i++) {
           
            PdfPage page = doc.getPage(i).copyTo(mergedPdf);
            mergedPdf.addPage(page);
            
        }
    }

    Rectangle pageSize = PageSize.A4;
    Rectangle pageBodySize = pageSize.clone().applyMargins(6,6,false);
    scale(mergedPdf,pageSize,pageBodySize);
    mergedPdf.close();

这工作正常，但是我所有的页面都有水印，并且缩放后的该水印几乎被放置在页面的中心，因此在缩放比例后，我需要在每个页面的底部设置页面的水印。 Pdf到A4。

我该如何实现？

编辑：我以这种方式添加水印：

 private byte[] addWatermark(final byte[] content,final String watermarkText,final Integer[] RgbColor,final Integer position) {
    final ByteArrayOutputStream pdfByteArrayOutputStream = new ByteArrayOutputStream();
    byte[] newPdfContent = new byte[0];
    Document document = null;

    try {
        document = createPdf(content,pdfByteArrayOutputStream);
        final Paragraph watermark = createWaterMark(watermarkText,RgbColor);
        addWatermarkToDocumentPages(document,watermark,position);
    } catch (final IOException e) {
        LOG.error("Error while adding watermark to Shipping Label,",e);
    } finally {
        if (Objects.nonNull(document)) {
            document.close();
            newPdfContent = pdfByteArrayOutputStream.toByteArray();
        }
    }

    return newPdfContent;
}

编辑2：

addWatermarkToDocumentPages执行以下操作：

 private void addWatermarkToDocumentPages(final Document document,final Paragraph watermark,final Integer position) {
    final PdfDocument pdfDocument = document.getPdfDocument();
    final int pages = pdfDocument.getNumberOfPages();

    // transparency
    final PdfExtGState gs1 = new PdfExtGState();
    gs1.setFillOpacity(0.9f);

    for (int i = 1; i <= pages; i++) {
        final PdfCanvas canvas = new PdfCanvas(pdfDocument.getPage(i));
        final PdfPage pdfPage = pdfDocument.getPage(i);
        final Rectangle pageSize = pdfPage.getPageSizeWithRotation();
        pdfPage.setIgnorePageRotationForContent(true);

        pageSize.increaseHeight(WATERMARK_MARGIN_SIZE);
        pageSize.moveDown(WATERMARK_MARGIN_SIZE);
        pdfPage.setMediaBox(pageSize);

        final float x = (pageSize.getLeft() + pageSize.getRight()) / 2;
        canvas.saveState();
        canvas.setExtGState(gs1);
        document.showTextAligned(watermark,x,position,TextAlignment.CENTER,VerticalAlignment.MIDDLE,0);
        canvas.restoreState();
    }
}

编辑3：

这是我的createPdf方法

private Document createPdf(final byte[] content,final ByteArrayOutputStream outputStream) throws IOException {
    try {
        final PdfDocument pdfDocument = new PdfDocument(new PdfReader(new ByteArrayInputStream(content)),new PdfWriter(outputStream));
        return new Document(pdfDocument);
    } catch (final IOException e) {
        throw new IOException("Error while creating the PDF Document,e);
    }
}