[英]JPedal - Highlight word at a point in a PDF
我想實現一個功能,該功能允許用戶雙擊以使用JPedal庫突出顯示PDF文檔中的單詞。 如果我可以得到一個單詞的邊界矩形並查看MouseEvent位置是否在其中,這將是微不足道的。 以下代碼段演示了如何突出顯示區域:
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();
}
但是,我只能在文檔中找到明文提取示例。
在查看了Mark的示例后,我設法使其正常運行。 有一些怪癖,所以我會解釋一下這一切如何工作,以防它對其他人有幫助。 關鍵方法是extractTextAsWordlist
,當給定要提取的區域時,它以{word1, w1_x1, w1_y1, w1_x2, w1_y2, word2, w2_x1, ...}
的形式返回List<String>
。 下面列出了分步說明。
首先,您需要將MouseEvent
“組件/屏幕”坐標轉換為PDF頁面坐標並進行縮放:
/**
* 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);
}
接下來,創建一個框以掃描文本。 我選擇將其寬度設置為垂直於MouseEvent
的頁面寬度和+/- 20個頁面單位(這是一個相當任意的數字):
/**
* 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,我將其解析為一個Rectangle
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;
}
然后確定MouseEvent
屬於哪個Rectangle
:
/**
* 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;
}
由於某種原因,僅將此Rectangle傳遞給突出顯示方法不起作用。 經過一番修補后,我發現將Rectangle
的每一邊縮小一點可以解決問題:
/**
* 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,我將其傳遞給此方法以添加亮點:
/**
* Highlights text on the document
*/
private void highlightText(Rectangle highlightRectangle) {
pdfDecoder.getTextLines().addHighlights(new Rectangle[]{highlightRectangle}, false, currentPage);
pdfDecoder.repaint();
}
最后,將上述所有調用打包到此便捷方法中:
/**
* 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();
}
}
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