comment or highlight two-column pdf using pdf-clown

Question

I have searched for possible solution by googling/so/forums for pdfClown/pdfbox and posting the problem at SO.

Problem: I have been trying to find a solution to highlight text, which spans across multiple lines in pdf document. The pdf can have one/two-column pages.

By using pdf-clown, I was able to highlight phrases, ONLY if all the words appear in the same line. pdfBox has created the XML for individual words, I could not find solution for phrases/lines.

Please suggest solution for pdf-clown, if any. (or) any other tool that is capable of highlighting text in multiple lines in pdf, with JAVA compatibility.

I could not understand the answer similar question, but iText, any help?: Multiline markup annotations with iText

Answer 1

Multi-column text is, at the moment (PDF Clown 0.1.2), not supported for extraction: the current algorithm gathers text laying on the same horizontal baseline without evaluating possible gaps between columns.

Automatic multi-column-layout detection would be possible yet somewhat tricky , as PDF is essentially (you know) an unstructured graphic format. Nonetheless, I'm considering to experiment something about that , in order to deal at least with the most common scenarios.

In the meantime, I can suggest you to try an effective workaround (it implies that you work on a document whose columns are placed in predictable areas): for each column do a separate text extraction , instructing the TextExtractor to look into the corresponding page area, then put all those partial extraction results together and apply your filter.

Answer 2

it is possible to get the coordinates of each word in a pdf document using pdfbox, here is the code for it:

import java.io.*;
import org.apache.pdfbox.exceptions.InvalidPasswordException;

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.common.PDStream;
import org.apache.pdfbox.util.PDFTextStripper;
import org.apache.pdfbox.util.TextPosition;

import java.io.IOException;
import java.util.List;

public class PrintTextLocations extends PDFTextStripper {

    public PrintTextLocations() throws IOException {
        super.setSortByPosition(true);
    }

    public static void main(String[] args) throws Exception {

        PDDocument document = null;
        try {
            File input = new File("C:\\path\\to\\PDF.pdf");
            document = PDDocument.load(input);
            if (document.isEncrypted()) {
                try {
                    document.decrypt("");
                } catch (InvalidPasswordException e) {
                    System.err.println("Error: Document is encrypted with a password.");
                    System.exit(1);
                }
            }
            PrintTextLocations printer = new PrintTextLocations();
            List allPages = document.getDocumentCatalog().getAllPages();
            for (int i = 0; i < allPages.size(); i++) {
                PDPage page = (PDPage) allPages.get(i);
                System.out.println("Processing page: " + i);
                PDStream contents = page.getContents();
                if (contents != null) {
                    printer.processStream(page, page.findResources(), page.getContents().getStream());
                }
            }
        } finally {
            if (document != null) {
                document.close();
            }
        }
    }

    protected void processTextPosition(TextPosition text) {
        System.out.println("String[" + text.getXDirAdj() + ","
                + text.getYDirAdj() + " fs=" + text.getFontSize() + " xscale="
                + text.getXScale() + " height=" + text.getHeightDir() + " space="
                + text.getWidthOfSpace() + " width="
                + text.getWidthDirAdj() + "]" + text.getCharacter());
    }
}