java - PDFbox 1.7.0 - 如何在使用 PDFBox 添加新图像的同时保留现有图像？

Question

我正在使用 PDFBox 1.7.0(由于生产服务器中的版本较旧，我无法选择该版本)。我正在尝试将图像添加到已有 Logo 的现有 PDF 中。当我添加新图像时，旧图像就像被替换一样消失了。

// Use for convert mm to dots
// ... 72 dots per inch
static final int DEFAULT_USER_SPACE_UNIT_DPI = 72;
// ... mm -> inch -> dots
static final float MM_TO_UNITS = 1 / (10 * 2.54f) * DEFAULT_USER_SPACE_UNIT_DPI;

/**
 * Add a given image to a specific page of a PDF
 * @param document PDF document to manipulate
 * @param input image inputStream
 * @param pdfpage page number to target
 * @param x image position (en mm)
 * @param y image position (en mm)
 * @param width max width of the image (mm)
 * @param height max height of the image (en mm)
 * @param opacity opacity level of the image (fraction)
 */
void addImageToPage (PDDocument document, InputStream input, int pdfpage, int x, int y, int width, int height, float opacity) throws IOException {
    if (input != null) {
        // Convert inputstream to usable BufferedImage
        BufferedImage tmp_image = ImageIO.read (input);
        // User TYPE_4BYTE_ABGR to fix PDFBox issue with transparent PNG
        BufferedImage image = new BufferedImage (tmp_image.getWidth(), tmp_image.getHeight(), BufferedImage.TYPE_4BYTE_ABGR);
        // Prepare the image
        image.createGraphics().drawRenderedImage (tmp_image, null);
        PDXObjectImage ximage = new PDPixelMap (document, image);
        // Resize the image
        int iWidth = ximage.getWidth();
        int iHeight = ximage.getHeight();
        if (width / height > iWidth / iHeight) {
            ximage.setWidth (Math.round (width * MM_TO_UNITS));
            ximage.setHeight (Math.round ((iHeight * width / iWidth) * MM_TO_UNITS));
        } else {
            ximage.setWidth (Math.round ((iWidth * height / iHeight) * MM_TO_UNITS));
            ximage.setHeight (Math.round (height * MM_TO_UNITS));
        }
        // Retrieve the page to update
        PDPage page = (PDPage)document.getDocumentCatalog().getAllPages().get (pdfpage);
        PDResources resources = page.findResources();
        // Get graphics states
        Map graphicsStates = resources.getGraphicsStates();
        if (graphicsStates == null) {
            graphicsStates = new HashMap();
        }
        // Set graphics states configurations
        PDExtendedGraphicsState extendedGraphicsState = new PDExtendedGraphicsState();
        // Set the opacity of the image
        extendedGraphicsState.setNonStrokingAlphaConstant (opacity);
        graphicsStates.put ("TransparentState", extendedGraphicsState);
        // Restore graphics states
        resources.setGraphicsStates (graphicsStates);
        // Retrieve the content stream
        PDPageContentStream contentStream = new PDPageContentStream (document, page, true, true);
        // Activate transparency options
        contentStream.appendRawCommands ("/TransparentState gs\n");
        contentStream.endMarkedContentSequence();
        // Insert image
        contentStream.drawImage (
            ximage,
            (float) x * MM_TO_UNITS,
            (float) y * MM_TO_UNITS
        );
        // close the stream
        contentStream.close();
    }
}

我希望页面内有新图像，但页面内的现有图像已经消失，而不是新图像。

使用的 PDF 示例:http://www.mediafire.com/folder/g6p7c2b5ob1c7/PDFBox_issue

Answer 1

1.7 中有几个错误...一个是我在评论中提到的(事实证明它不会影响您)，另一个是资源进行了一些缓存但没有正确管理...长话短说，您需要像这样保存和恢复您的 xobject 资源:

Map<String, PDXObject> xObjectsMap = page.getResources().getXObjects(); // save xobjects
…
PDXObjectImage ximage = new PDPixelMap (document, image);
String imgName = page.getResources().addXObject(ximage, "Im");
cs.drawImage(ximage, 0, 0); // bug happens here, old xobjects gets lost
xObjectsMap.put(imgName, ximage);
page.getResources().setXObjects(xObjectsMap); // restore xobjects

这实际上只是一个解决方法......可能会有更多糟糕的意外发生。您不应该使用旧版本。他们不再激发欢乐。你应该感谢他们的服务，然后毫无愧疚地让他们离开。