PDFBox-直线/矩形提取

Question

我试图从PDF中提取文本坐标和直线（或矩形）坐标。

TextPosition类有getXDirAdj（）和getYDirAdj（）方法，这些方法根据各自TextPosition对象表示的文本块的方向转换坐标（根据@mkl的注释进行更正）。最终输出是一致的，与页面旋转无关。

输出所需的坐标为X0，Y0（页面左上角）

这是对@Tilman Hausherr的解决方案的轻微修改。y坐标被反转（高度-y），以保持其与文本提取过程中的坐标一致，并且输出被写入csv。

    public class LineCatcher extends PDFGraphicsStreamEngine
{
    private static final GeneralPath linePath = new GeneralPath();
    private static ArrayList<Rectangle2D> rectList= new ArrayList<Rectangle2D>();
    private int clipWindingRule = -1;
    private static String headerRecord = "Text|Page|x|y|width|height|space|font";

    public LineCatcher(PDPage page)
    {
        super(page);
    }

    public static void main(String[] args) throws IOException
    {
        if( args.length != 4 )
        {
            usage();
        }
        else
        {
            PDDocument document = null;
            FileOutputStream fop = null;
            File file;
            Writer osw = null;
            int numPages;
            double page_height;
            try
            {
                document = PDDocument.load( new File(args[0], args[1]) );
                numPages = document.getNumberOfPages();
                file = new File(args[2], args[3]);
                fop = new FileOutputStream(file);

                // if file doesnt exists, then create it
                if (!file.exists()) {
                    file.createNewFile();
                }

                osw = new OutputStreamWriter(fop, "UTF8");
                osw.write(headerRecord + System.lineSeparator());
                System.out.println("Line Processing numPages:" + numPages);
                for (int n = 0; n < numPages; n++) {
                    System.out.println("Line Processing page:" + n);
                    rectList = new ArrayList<Rectangle2D>();
                    PDPage page = document.getPage(n);
                    page_height = page.getCropBox().getUpperRightY();
                    LineCatcher lineCatcher = new LineCatcher(page);
                    lineCatcher.processPage(page);

                    try{
                        for(Rectangle2D rect:rectList) {

                            String pageNum = Integer.toString(n + 1);
                            String x = Double.toString(rect.getX());
                            String y = Double.toString(page_height - rect.getY()) ;
                            String w = Double.toString(rect.getWidth());
                            String h = Double.toString(rect.getHeight());
                            writeToFile(pageNum, x, y, w, h, osw);

                        }
                        rectList = null;
                        page = null;
                        lineCatcher = null;
                    }
                    catch(IOException io){
                        throw new IOException("Failed to Parse document for line processing. Incorrect document format. Page:" + n);
                    }
                };

            }
            catch(IOException io){
                throw new IOException("Failed to Parse document for line processing. Incorrect document format.");
            }
            finally
            {
                if ( osw != null ){
                    osw.close();
                }
                if( document != null )
                {
                    document.close();
                }
            }
        }
    }

    private static void writeToFile(String pageNum, String x, String y, String w, String h, Writer osw) throws IOException {
        String c = "^" + "|" +
                pageNum + "|" +
                x + "|" +
                y + "|" +
                w + "|" +
                h + "|" +
                "999" + "|" +
                "marker-only";
        osw.write(c + System.lineSeparator());
    }

    @Override
    public void appendRectangle(Point2D p0, Point2D p1, Point2D p2, Point2D p3) throws IOException
    {
        // to ensure that the path is created in the right direction, we have to create
        // it by combining single lines instead of creating a simple rectangle
        linePath.moveTo((float) p0.getX(), (float) p0.getY());
        linePath.lineTo((float) p1.getX(), (float) p1.getY());
        linePath.lineTo((float) p2.getX(), (float) p2.getY());
        linePath.lineTo((float) p3.getX(), (float) p3.getY());

        // close the subpath instead of adding the last line so that a possible set line
        // cap style isn't taken into account at the "beginning" of the rectangle
        linePath.closePath();
    }

    @Override
    public void drawImage(PDImage pdi) throws IOException
    {
    }

    @Override
    public void clip(int windingRule) throws IOException
    {
        // the clipping path will not be updated until the succeeding painting operator is called
        clipWindingRule = windingRule;

    }

    @Override
    public void moveTo(float x, float y) throws IOException
    {
        linePath.moveTo(x, y);
    }

    @Override
    public void lineTo(float x, float y) throws IOException
    {
        linePath.lineTo(x, y);
    }

    @Override
    public void curveTo(float x1, float y1, float x2, float y2, float x3, float y3) throws IOException
    {
        linePath.curveTo(x1, y1, x2, y2, x3, y3);
    }

    @Override
    public Point2D getCurrentPoint() throws IOException
    {
        return linePath.getCurrentPoint();
    }

    @Override
    public void closePath() throws IOException
    {
        linePath.closePath();
    }

    @Override
    public void endPath() throws IOException
    {
        if (clipWindingRule != -1)
        {
            linePath.setWindingRule(clipWindingRule);
            getGraphicsState().intersectClippingPath(linePath);
            clipWindingRule = -1;
        }
        linePath.reset();

    }

    @Override
    public void strokePath() throws IOException
    {
        rectList.add(linePath.getBounds2D());
        linePath.reset();
    }

    @Override
    public void fillPath(int windingRule) throws IOException
    {
        linePath.reset();
    }

    @Override
    public void fillAndStrokePath(int windingRule) throws IOException
    {
        linePath.reset();
    }

    @Override
    public void shadingFill(COSName cosn) throws IOException
    {
    }

    /**
     * This will print the usage for this document.
     */
    private static void usage()
    {
        System.err.println( "Usage: java " + LineCatcher.class.getName() + " <input-pdf>"  + " <output-file>");
    }
}

正在使用PDFGraphicsStreamEngine类来提取线条和矩形坐标。线条和矩形的坐标与文本的坐标不一致

绿色：文本红色：获得黑色的线条坐标：预期坐标（在输出上应用转换后获得）

在运行行提取之前，尝试了setRotation（）方法来纠正旋转。然而，结果并不一致。

使用PDFBox获得旋转并获得一致的直线/矩形坐标输出的可能选项有哪些？

Answer 1

就我所理解的需求而言，OP工作在一个坐标系中，原点在可见页面的左上角（考虑到页面旋转），x坐标向右增加，y坐标向下增加，单位是PDF默认用户空间单位（通常为¹/₇₂英寸）。

在这个坐标系中，他需要以

• 左/上endpoint和

另一方面，他从蒂尔曼那里得到的帮助类LineCatcher不考虑页面旋转。此外，它返回垂直线的底部终端，而不是顶部终端。因此，必须对LineCatcher结果应用坐标转换。

为此，只需更换

for(Rectangle2D rect:rectList) {
    String pageNum = Integer.toString(n + 1);
    String x = Double.toString(rect.getX());
    String y = Double.toString(page_height - rect.getY()) ;
    String w = Double.toString(rect.getWidth());
    String h = Double.toString(rect.getHeight());
    writeToFile(pageNum, x, y, w, h, osw);
}

通过

int pageRotation = page.getRotation();
PDRectangle pageCropBox = page.getCropBox();

for(Rectangle2D rect:rectList) {
    String pageNum = Integer.toString(n + 1);
    String x, y, w, h;
    switch(pageRotation) {
    case 0:
        x = Double.toString(rect.getX() - pageCropBox.getLowerLeftX());
        y = Double.toString(pageCropBox.getUpperRightY() - rect.getY() + rect.getHeight());
        w = Double.toString(rect.getWidth());
        h = Double.toString(rect.getHeight());
        break;
    case 90:
        x = Double.toString(rect.getY() - pageCropBox.getLowerLeftY());
        y = Double.toString(rect.getX() - pageCropBox.getLowerLeftX());
        w = Double.toString(rect.getHeight());
        h = Double.toString(rect.getWidth());
        break;
    case 180:
        x = Double.toString(pageCropBox.getUpperRightX() - rect.getX() - rect.getWidth());
        y = Double.toString(rect.getY() - pageCropBox.getLowerLeftY());
        w = Double.toString(rect.getWidth());
        h = Double.toString(rect.getHeight());
        break;
    case 270:
        x = Double.toString(pageCropBox.getUpperRightY() - rect.getY() + rect.getHeight());
        y = Double.toString(pageCropBox.getUpperRightX() - rect.getX() - rect.getWidth());
        w = Double.toString(rect.getHeight());
        h = Double.toString(rect.getWidth());
        break;
    default:
        throw new IOException(String.format("Unsupported page rotation %d on page %d.", pageRotation, page));
    }
    writeToFile(pageNum, x, y, w, h, osw);
}

（ExtratLinesRevDir testtestExtratLineRotationTestRevDir）

OP通过引用TextPosition类方法getXDirAdj（）和getYDirAdj（）来描述坐标。实际上，这些方法返回坐标系中的坐标，原点在页面左上角，y坐标在旋转页面后向下增加，以便垂直绘制文本。

在示例文档的情况下，所有的文本都被绘制成在应用页面旋转后直立的。从这一点出发，我对写在顶部的要求的理解已经得到了推导。

然而，使用TextPosition.get?DirAdj（）值作为全局坐标的问题在于，在文本以不同方向绘制的页面中，收集的文本坐标突然相对于不同的坐标系。因此，一般的解决方案不应该像这样疯狂地收集坐标。相反，它应该首先确定页面方向（例如页面旋转给出的方向或大多数文本共享的方向），并使用该方向给出的固定坐标系中的坐标加上所讨论的文本的书写方向的指示。