PDFBox extension to extract previously tagged math areas from a PDF document

ExtractMath.java

package org.apache.pdfbox;

import org.apache.pdfbox.exceptions.InvalidPasswordException;

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.interactive.annotation.PDAnnotation;
import org.apache.pdfbox.pdmodel.common.PDRectangle;
import org.apache.pdfbox.util.PDFTextStripperByArea;

import java.awt.geom.Rectangle2D;

import java.util.List;

public class ExtractMath
{
    // ExtractMath is a namespace
    private ExtractMath() {}

    public static void main(String[] args) throws Exception
    {
        int argc = args.length;
        if (argc < 1) {
            usage();
            return;
        }

        PDDocument document = null;
        float yOffset   = 0.0f;
        float addHeight = 0.0f;
        try {
            document = PDDocument.load(args[0]);
            if (argc > 1) {
                yOffset = Float.parseFloat(args[1]);
                if (argc > 2)
                    addHeight = Float.parseFloat(args[2]);
            }

            if (document.isEncrypted()) {
                try {
                    document.decrypt( "" );
                    
                } catch( InvalidPasswordException e ) {
                        System.err.println( "Error: Document is encrypted with a password." );
                        System.exit( 1 );
                }
            }

            List<PDPage> allPages = document.getDocumentCatalog().getAllPages();
            int pageIdx = 0;
            for (PDPage page : allPages) {
                PDFTextStripperByArea stripper = new PDFTextStripperByArea();
                stripper.setSortByPosition(true);

                PDRectangle cropBox = page.findCropBox();
                System.out.println("Crop box for page " + pageIdx + ": "+ cropBox);
                PDRectangle mediaBox = page.findMediaBox();
                System.out.println("Media box for this page: " + pageIdx + ": " + mediaBox);

                List<PDAnnotation> pageAnnotations = page.getAnnotations();
                int formulaIdx = 0;
                for(PDAnnotation annot: pageAnnotations) {
                    if ("MathML".equals(annot.getSubtype())) {
                        PDRectangle pdRect = annot.getRectangle();
                        float h = pdRect.getHeight() + addHeight;
                        float w = pdRect.getWidth();
                        float y = mediaBox.getHeight() - pdRect.getLowerLeftY() - h + yOffset;
                        Rectangle2D rect = new Rectangle2D.Float();
                        rect.setRect(pdRect.getLowerLeftX()-0.01f, y + 0.01f, w, h);
                        System.out.println("define region: " + rect);
                        stripper.addRegion("formula"+formulaIdx, rect);
                        formulaIdx += 1;
                    }
                }

                stripper.extractRegions(page);
                formulaIdx = 0;
                for(PDAnnotation annot: pageAnnotations) {
                    if ("MathML".equals(annot.getSubtype())) {
                        System.out.println("MathML formula:");
                        System.out.println(annot.getContents());
                        PDRectangle pdRect = annot.getRectangle();
                        System.out.println("Text in the area: " + pdRect);
                        System.out.println(stripper.getTextForRegion("formula"+formulaIdx));
                        formulaIdx += 1;
                    }
                }
            }
        }
        finally {
            if (document != null)
                document.close();
        }
    }

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

}

This file needs to be placed inside the src/main/java/org/apache/pdfbox folder. Additionally, PDFBox.java needs to be modified to include the new ExtractMath command:

        try {
            if (command.equals("ConvertColorspace")) {
                ConvertColorspace.main(arguments);
            } else if (command.equals("Decrypt")) {
                Decrypt.main(arguments);
            } else if (command.equals("Encrypt")) {
                Encrypt.main(arguments);
            } else if (command.equals("ExtractText")) {
                ExtractText.main(arguments);
            } else if (command.equals("ExtractMath")) {
                ExtractMath.main(arguments);