Javax.swing.text、Lowagie、HTMLWriter 添加图像(不是来自文件)

Question

我正在尝试在 Java 的 com.lowagie.text 中使用 htmlWriter 创建一个文档。我所做的是创建一个图像(来自二维码)并尝试将其添加到文档中。文档连接到 ByteArrayOutputStream，然后我将其写出到 ServletOutputStream。

当我从位矩阵创建图像时，没有任何反应。我想知道这是否是因为 html 需要图像 URL。因此，如果我从 url 获取图像，它就会显示。但是当我只是在 java 中创建一个图像时，它不会在 html 中显示这个？!？谁能帮帮我？

 public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    // setting some response headers
    response.setHeader("Expires", EXPIRES);

    // setting the content type
    response.setContentType(CONTENT_TYPE);

    ServletOutputStream out = null;
    ByteArrayOutputStream baos = null;
    try {
        baos = getHtmlTicket();

        // write ByteArrayOutputStream to the ServletOutputStream
        out = response.getOutputStream();
        baos.writeTo(out);
    }
    catch (Exception e) {

        log.error(e.getMessage(), e);
        response.setContentType("text/html");
        // response.setHeader("Content-Disposition", "filename=\"" + filename + "\"");
        response.getWriter().write("<p>Det har oppst�tt en feil!</p>");
        response.getWriter().write("<p>" + new Date().toString() + "</p>");
        response.getWriter().write("<!-- " + e.getMessage() + " -->");
        response.flushBuffer();
    }


   public ByteArrayOutputStream getHtmlTicket() {
    ByteArrayOutputStream baos = new ByteArrayOutputStream(); 

    Document document = new Document();

    String myCodeText = "YO YOU";
    int size = 128;
    try {
        HtmlWriter.getInstance(document, baos);
        document.open();
        document.add(new Paragraph("Hello World"));
        document.add(new Paragraph(new Date().toString()));

        Hashtable<EncodeHintType, ErrorCorrectionLevel> hintMap = new Hashtable<EncodeHintType, ErrorCorrectionLevel>();
        hintMap.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.L);
        QRCodeWriter qrCodeWriter = new QRCodeWriter();
        BitMatrix byteMatrix = qrCodeWriter.encode(myCodeText,BarcodeFormat.QR_CODE, size, size, hintMap);
        int pictureWidth = byteMatrix.getWidth();
        BufferedImage bimage = new BufferedImage(pictureWidth, pictureWidth,
                BufferedImage.TYPE_INT_RGB);
        bimage.createGraphics();

        Graphics2D graphics = (Graphics2D) bimage.getGraphics();
        graphics.setColor(Color.WHITE);
        graphics.fillRect(0, 0, pictureWidth, pictureWidth);
        graphics.setColor(Color.BLACK);

        for (int i = 0; i < pictureWidth; i++) {
            for (int j = 0; j < pictureWidth; j++) {
                if (byteMatrix.get(i, j)) {
                    graphics.fillRect(i, j, 1, 1);
                }
            }
        }

        com.lowagie.text.Image image = com.lowagie.text.Image.getInstance(bimage , null); 
        document.add(image);


    }
    catch (DocumentException e) {
        e.printStackTrace();
    } catch (MalformedURLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    catch (WriterException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    document.close();

    return baos;
}

Answer 1

创建 HtmlWriter 是为了在开发过程中测试 Itext 库。这就是为什么图像只显示为没有内容的正方形的原因。这也是 Itext 的创建者在以后的版本中删除 htmlWriter 的原因。

如果您希望响应以 HTML 格式显示图像(必须是 bufferedImage)，您可以像这样将图像转换为 Base64:

 private String addImageToHTML(BufferedImage bf) {
    String base64String = "";
    ByteArrayOutputStream baos = new ByteArrayOutputStream(); 
    try {
        ImageIO.write(bf, "png", baos);
        base64String = DatatypeConverter.printBase64Binary(baos.toByteArray());
    }
    catch (IOException e) {
        e.printStackTrace();
    } 
    return "<img style='max-width:100%' src='data:image/png;base64,"+ base64String + "' alt='IMG DESC'/>";
  }