Question

我想实现一个功能，允许用户使用JPedal库双击突出显示PDF文档中的单词。如果我能得到一个单词的边界矩形并查看MouseEvent位置是否属于它，那么这将是微不足道的。以下代码段演示了如何突出显示某个区域：

private void highlightText() {
    Rectangle highlightRectangle = new Rectangle(firstPoint.x, firstPoint.y,
            secondPoint.x - firstPoint.x, secondPoint.y - firstPoint.y);
    pdfDecoder.getTextLines().addHighlights(new Rectangle[]{highlightRectangle}, false, currentPage);
    pdfDecoder.repaint();
}

我只能在文档中找到明文提取示例。

Answer 1

在看了Mark的例子后，我设法让它运转起来。有一些怪癖，所以我会解释它是如何工作的，以防它帮助其他人。关键方法是extractTextAsWordlist，当给定要从中提取的区域时，它会返回List<String>形式的{word1, w1_x1, w1_y1, w1_x2, w1_y2, word2, w2_x1, ...}。下面列出了分步说明。

首先，您需要将MouseEvent的组件/屏幕坐标转换为PDF页面坐标并校正缩放：

/**
 * Transforms Component coordinates to page coordinates, correcting for 
 * scaling and panning.
 * 
 * @param x Component x-coordinate
 * @param y Component y-coordinate
 * @return Point on the PDF page
 */
private Point getPageCoordinates(int x, int y) {
    float scaling = pdfDecoder.getScaling();
    int x_offset = ((pdfDecoder.getWidth() - pdfDecoder.getPDFWidth()) / 2); 
    int y_offset = pdfDecoder.getPDFHeight();
    int correctedX = (int)((x - x_offset + viewportOffset.x) / scaling);
    int correctedY = (int)((y_offset - (y + viewportOffset.y))  / scaling);
    return new Point(correctedX, correctedY);
}

接下来，创建一个用于扫描文本的框。我选择将页面的宽度和+/- 20页面单位垂直（这是一个相当任意的数字），以MouseEvent为中心：

/**
 * Scans for all the words located with in a box the width of the page and 
 * 40 points high, centered at the supplied point.
 * 
 * @param p Point to centre the scan box around
 * @return  A List of words within the scan box
 * @throws PdfException
 */
private List<String> scanForWords(Point p) throws PdfException {
    List<String> result = Collections.emptyList();
    if (pdfDecoder.getlastPageDecoded() > 0) {
        PdfGroupingAlgorithms currentGrouping = pdfDecoder.getGroupingObject();
        PdfPageData currentPageData = pdfDecoder.getPdfPageData();
        int x1 = currentPageData.getMediaBoxX(currentPage);
        int x2 = currentPageData.getMediaBoxWidth(currentPage) + x1;
        int y1 = p.y + 20;
        int y2 = p.y - 20;
        result = currentGrouping.extractTextAsWordlist(x1, y1, x2, y2, currentPage, true, "");
    }
    return result;
}

然后我将其解析为Rectangle s：

的序列

/**
 * Parse a String sequence of:
 *   {word1, w1_x1, w1_y1, w1_x2, w1_y2, word2, w2_x1, ...}
 *   
 * Into a sequence of Rectangles.
 * 
 * @param wordList Word list sequence to parse
 * @return A List of Rectangles
 */
private List<Rectangle> parseWordBounds(List<String> wordList) {
    List<Rectangle> wordBounds = new LinkedList<Rectangle>();
    Iterator<String> wordListIterator = wordList.iterator();
    while(wordListIterator.hasNext()) {
        // sequences are: {word, x1, y1, x2, y2}  
        wordListIterator.next(); // skip the word
        int x1 = (int) Float.parseFloat(wordListIterator.next());
        int y1 = (int) Float.parseFloat(wordListIterator.next());
        int x2 = (int) Float.parseFloat(wordListIterator.next());
        int y2 = (int) Float.parseFloat(wordListIterator.next());
        wordBounds.add(new Rectangle(x1, y2, x2 - x1, y1 - y2)); // in page, not screen coordinates
    }
    return wordBounds;
}

然后确定了Rectangle MouseEvent落入的内容：

/**
 * Finds the bounding Rectangle of a word located at a Point.
 * 
 * @param p Point to find word bounds
 * @param wordBounds List of word boundaries to search
 * @return A Rectangle that bounds a word and contains a point, or null if 
 *         there is no word located at the point
 */
private Rectangle findWordBoundsAtPoint(Point p, List<Rectangle> wordBounds) {
    Rectangle result = null;
    for (Rectangle wordBound : wordBounds) {
        if (wordBound.contains(p)) {
            result = wordBound;
            break;
        }
    }
    return result;
}

由于某种原因，只是将此Rectangle传递给突出显示方法不起作用。经过一些修修补补后，我发现每个方面的Rectangle缩小了一个点就解决了问题：

/**
 * Contracts a Rectangle to enable it to be highlighted.
 * 
 * @return A contracted Highlight Rectangle
 */
private Rectangle contractHighlight(Rectangle highlight){
    int x = highlight.x + 1;
    int y = highlight.y + 1;
    int width = highlight.width -2;
    int height = highlight.height - 2;
    return new Rectangle(x, y, width, height);
}

然后我把它传递给这个方法来添加亮点：

/**
 * Highlights text on the document
 */
private void highlightText(Rectangle highlightRectangle) {
    pdfDecoder.getTextLines().addHighlights(new Rectangle[]{highlightRectangle}, false, currentPage);
    pdfDecoder.repaint();
}

最后，所有上述调用都包含在这个方便的方法中：

/**
 * Highlights the word at the given point.
 * 
 * @param p Point where word is located
 */
private void highlightWordAtPoint(Point p) {
    try {
        Rectangle wordBounds = findWordBoundsAtPoint(p, parseWordBounds(scanForWords(p)));
        if (wordBounds != null) {
            highlightText(contractHighlight(wordBounds));
        }
    } catch (PdfException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

JPedal - 突出显示PDF中某个点的单词

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