Could someone give me an example of how to extract coordinates for a 'word' using PDFBox

Question

Could someone give me an example of how to extract coordinates for a \'word\' with PDFBox

I am using this link to extract positions of individual characters: https:/

Answer 1

You can extract the coordinates of words by collecting all the TextPosition objects building a word and combining their bounding boxes.

Implementing this along the lines of the two tutorials you referenced, you can extend PDFTextStripper like this:

public class GetWordLocationAndSize extends PDFTextStripper {
    public GetWordLocationAndSize() throws IOException {
    }

    @Override
    protected void writeString(String string, List<TextPosition> textPositions) throws IOException {
        String wordSeparator = getWordSeparator();
        List<TextPosition> word = new ArrayList<>();
        for (TextPosition text : textPositions) {
            String thisChar = text.getUnicode();
            if (thisChar != null) {
                if (thisChar.length() >= 1) {
                    if (!thisChar.equals(wordSeparator)) {
                        word.add(text);
                    } else if (!word.isEmpty()) {
                        printWord(word);
                        word.clear();
                    }
                }
            }
        }
        if (!word.isEmpty()) {
            printWord(word);
            word.clear();
        }
    }

    void printWord(List<TextPosition> word) {
        Rectangle2D boundingBox = null;
        StringBuilder builder = new StringBuilder();
        for (TextPosition text : word) {
            Rectangle2D box = new Rectangle2D.Float(text.getXDirAdj(), text.getYDirAdj(), text.getWidthDirAdj(), text.getHeightDir());
            if (boundingBox == null)
                boundingBox = box;
            else
                boundingBox.add(box);
            builder.append(text.getUnicode());
        }
        System.out.println(builder.toString() + " [(X=" + boundingBox.getX() + ",Y=" + boundingBox.getY()
                 + ") height=" + boundingBox.getHeight() + " width=" + boundingBox.getWidth() + "]");
    }
}

(ExtractWordCoordinates inner class)

and run it like this:

PDDocument document = PDDocument.load(resource);
PDFTextStripper stripper = new GetWordLocationAndSize();
stripper.setSortByPosition( true );
stripper.setStartPage( 0 );
stripper.setEndPage( document.getNumberOfPages() );

Writer dummy = new OutputStreamWriter(new ByteArrayOutputStream());
stripper.writeText(document, dummy);

(ExtractWordCoordinates test testExtractWordsForGoodJuJu)

Applied to the apache.pdf example the tutorials use you get:

2017-8-6 [(X=26.004425048828125,Y=22.00372314453125) height=5.833024024963379 width=36.31868362426758]
Welcome [(X=226.44479370117188,Y=22.00372314453125) height=5.833024024963379 width=36.5999755859375]
to [(X=265.5881652832031,Y=22.00372314453125) height=5.833024024963379 width=8.032623291015625]
The [(X=276.1641845703125,Y=22.00372314453125) height=5.833024024963379 width=14.881439208984375]
Apache [(X=293.5890197753906,Y=22.00372314453125) height=5.833024024963379 width=29.848846435546875]
Software [(X=325.98126220703125,Y=22.00372314453125) height=5.833024024963379 width=35.271636962890625]
Foundation! [(X=363.7962951660156,Y=22.00372314453125) height=5.833024024963379 width=47.871429443359375]
Custom [(X=334.0334777832031,Y=157.6195068359375) height=4.546705722808838 width=25.03936767578125]
Search [(X=360.8929138183594,Y=157.6195068359375) height=4.546705722808838 width=22.702728271484375]

Answer 2

You can create CustomPDFTextStripper which extends PDFTextStripper and override protected void writeString(String text, List<TextPosition> textPositions). In this overriden method you need to split textPositions by the word separator to get List<TextPosition> for each word. After that you can join each character and compute bounding box.

Full example below which contains also drawing of the resulting bounding boxes.

package com.example;

import lombok.Value;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.rendering.PDFRenderer;
import org.apache.pdfbox.text.PDFTextStripper;
import org.apache.pdfbox.text.TextPosition;
import org.junit.Ignore;
import org.junit.Test;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.*;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

public class PdfBoxTest {

    private static final String BASE_DIR_PATH = "C:\\Users\\Milan\\50330484";
    private static final String INPUT_FILE_PATH = "input.pdf";
    private static final String OUTPUT_IMAGE_PATH = "output.jpg";
    private static final String OUTPUT_BBOX_IMAGE_PATH = "output-bbox.jpg";

    private static final float FROM_72_TO_300_DPI = 300.0f / 72.0f;

    @Test
    public void run() throws Exception {
        pdfToImage();
        drawBoundingBoxes();
    }

    @Ignore
    @Test
    public void pdfToImage() throws IOException {
        PDDocument document = PDDocument.load(new File(BASE_DIR_PATH, INPUT_FILE_PATH));
        PDFRenderer renderer = new PDFRenderer(document);
        BufferedImage image = renderer.renderImageWithDPI(0, 300);
        ImageIO.write(image, "JPEG", new File(BASE_DIR_PATH, OUTPUT_IMAGE_PATH));
    }

    @Ignore
    @Test
    public void drawBoundingBoxes() throws IOException {

        PDDocument document = PDDocument.load(new File(BASE_DIR_PATH, INPUT_FILE_PATH));

        List<WordWithBBox> words = getWords(document);

        draw(words);
    }

    private List<WordWithBBox> getWords(PDDocument document) throws IOException {

        CustomPDFTextStripper customPDFTextStripper = new CustomPDFTextStripper();
        customPDFTextStripper.setSortByPosition(true);
        customPDFTextStripper.setStartPage(0);
        customPDFTextStripper.setEndPage(1);

        Writer writer = new OutputStreamWriter(new ByteArrayOutputStream());
        customPDFTextStripper.writeText(document, writer);

        List<WordWithBBox> words = customPDFTextStripper.getWords();

        return words;
    }

    private void draw(List<WordWithBBox> words) throws IOException {

        BufferedImage bufferedImage = ImageIO.read(new File(BASE_DIR_PATH, OUTPUT_IMAGE_PATH));

        Graphics2D graphics = bufferedImage.createGraphics();

        graphics.setColor(Color.GREEN);

        List<Rectangle> rectangles = words.stream()
                .map(word -> new Rectangle(word.getX(), word.getY(), word.getWidth(), word.getHeight()))
                .collect(Collectors.toList());
        rectangles.forEach(graphics::draw);

        graphics.dispose();

        ImageIO.write(bufferedImage, "JPEG", new File(BASE_DIR_PATH, OUTPUT_BBOX_IMAGE_PATH));
    }

    private class CustomPDFTextStripper extends PDFTextStripper {

        private final List<WordWithBBox> words;

        public CustomPDFTextStripper() throws IOException {
            this.words = new ArrayList<>();
        }

        public List<WordWithBBox> getWords() {
            return new ArrayList<>(words);
        }

        @Override
        protected void writeString(String text, List<TextPosition> textPositions) throws IOException {

            String wordSeparator = getWordSeparator();
            List<TextPosition> wordTextPositions = new ArrayList<>();

            for (TextPosition textPosition : textPositions) {
                String str = textPosition.getUnicode();
                if (wordSeparator.equals(str)) {
                    if (!wordTextPositions.isEmpty()) {
                        this.words.add(createWord(wordTextPositions));
                        wordTextPositions.clear();
                    }
                } else {
                    wordTextPositions.add(textPosition);
                }
            }

            super.writeString(text, textPositions);
        }

        private WordWithBBox createWord(List<TextPosition> wordTextPositions) {

            String word = wordTextPositions.stream()
                    .map(TextPosition::getUnicode)
                    .collect(Collectors.joining());

            int minX = Integer.MAX_VALUE;
            int minY = Integer.MAX_VALUE;
            int maxX = Integer.MIN_VALUE;
            int maxY = Integer.MIN_VALUE;

            for (TextPosition wordTextPosition : wordTextPositions) {

                minX = Math.min(minX, from72To300Dpi(wordTextPosition.getXDirAdj()));
                minY = Math.min(minY, from72To300Dpi(wordTextPosition.getYDirAdj() - wordTextPosition.getHeightDir()));
                maxX = Math.max(maxX, from72To300Dpi(wordTextPosition.getXDirAdj() + wordTextPosition.getWidthDirAdj()));
                maxY = Math.max(maxY, from72To300Dpi(wordTextPosition.getYDirAdj()));
            }

            return new WordWithBBox(word, minX, minY, maxX - minX, maxY - minY);
        }
    }

    private int from72To300Dpi(float f) {
        return Math.round(f * FROM_72_TO_300_DPI);
    }

    @Value
    private class WordWithBBox {
        private final String word;
        private final int x;
        private final int y;
        private final int width;
        private final int height;
    }
}

Note:

If you are interested in other options, you can check also Poppler

PDF to image

pdftoppm -r 300 -jpeg input.pdf output

Generate an XHTML file containing bounding box information for each word in the file.

pdftotext -r 300 -bbox input.pdf