Extracting answers to a flattened PDF form with iText 7

Question

We have a few forms created from Adobe LiveCycle where users fill the dynamic forms and submits the document to our office where we stamp it with our signature and flatten it (at least most of the time - I've seen a few documents in our system that haven't been flattened yet but that can be a separate question, I'll focus on the flattened documents here because that's most of what we have).

I'm trying to use iText 7 to parse/extract the user's answers to our forms for migrating to an electronic solution that will happen a few months from now. I was able to make the example work in Java but I don't understand the process.

/*
    This file is part of the iText (R) project.
    Copyright (c) 1998-2020 iText Group NV
    Authors: iText Software.
 
    For more information, please contact iText Software at this address:
    sales@itextpdf.com
 */
/**
 * Example written by Bruno Lowagie in answer to:
 * http://stackoverflow.com/questions/24506830/can-we-use-text-extraction-strategy-after-applying-location-extraction-strategy
 */
package ca.umanitoba.ad.research;
 
import com.itextpdf.kernel.font.PdfFont;
import com.itextpdf.kernel.geom.Rectangle;
import com.itextpdf.kernel.pdf.PdfDocument;
import com.itextpdf.kernel.pdf.PdfReader;
import com.itextpdf.kernel.pdf.canvas.parser.EventType;
import com.itextpdf.kernel.pdf.canvas.parser.PdfCanvasProcessor;
import com.itextpdf.kernel.pdf.canvas.parser.data.IEventData;
import com.itextpdf.kernel.pdf.canvas.parser.data.TextRenderInfo;
import com.itextpdf.kernel.pdf.canvas.parser.filter.TextRegionEventFilter;
import com.itextpdf.kernel.pdf.canvas.parser.listener.FilteredEventListener;
import com.itextpdf.kernel.pdf.canvas.parser.listener.LocationTextExtractionStrategy;
 
import java.io.File;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.FileOutputStream;
import java.io.Writer;
import java.io.BufferedWriter;
 
public class Main {
    public static final String DEST = "./target/txt/parse_custom.txt";
 
    public static final String SRC = "./src/main/resources/pdfs/nameddestinations.pdf";
 
    public static void main(String[] args) throws IOException {
        File file = new File(DEST);
        file.getParentFile().mkdirs();
 
        new Main().manipulatePdf(DEST);
    }
 
    protected void manipulatePdf(String dest) throws IOException {
        PdfDocument pdfDoc = new PdfDocument(new PdfReader(SRC));
 
        Rectangle rect = new Rectangle(36, 750, 523, 56);
        CustomFontFilter fontFilter = new CustomFontFilter(rect);
        FilteredEventListener listener = new FilteredEventListener();
 
        // Create a text extraction renderer
        LocationTextExtractionStrategy extractionStrategy = listener
                .attachEventListener(new LocationTextExtractionStrategy(), fontFilter);
 
        // Note: If you want to re-use the PdfCanvasProcessor, you must call PdfCanvasProcessor.reset()
        PdfCanvasProcessor parser = new PdfCanvasProcessor(listener);
        parser.processPageContent(pdfDoc.getFirstPage());
 
        // Get the resultant text after applying the custom filter
        String actualText = extractionStrategy.getResultantText();
 
        pdfDoc.close();
 
        // See the resultant text in the console
        System.out.println(actualText);
 
        try (Writer writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(dest)))) {
            writer.write(actualText);
        }
    }
 
    /*
     * The custom filter filters only the text of which the font name ends with Bold or Oblique.
     */
    protected class CustomFontFilter extends TextRegionEventFilter {
        public CustomFontFilter(Rectangle filterRect) {
            super(filterRect);
        }
 
        @Override
        public boolean accept(IEventData data, EventType type) {
            if (type.equals(EventType.RENDER_TEXT)) {
                TextRenderInfo renderInfo = (TextRenderInfo) data;
                PdfFont font = renderInfo.getFont();
                if (null != font) {
                    String fontName = font.getFontProgram().getFontNames().getFontName();
                    return fontName.endsWith("Bold") || fontName.endsWith("Oblique");
                }
            }
 
            return false;
        }
    }
}

Why is there a need to specify a Rectangle? Our forms are dynamic so users can add more fields as needed and we also accept paragraphs on some of the questions so the length will always vary so it's unlikely that the coordinates of the texts will be the same.

How can I change the flow so that I can perhaps just search for the question and then get the text right after it (presumably the answer) - I don't really know what the best way to parse a PDF is. If there's no other way except providing a Rectangle, can I programmatically determine the coordinates/dimensions of the rectangles?

From the example it looks like it's filtering the text based on whether it's bolded or italicized which I probably don't need but it looks to be easy enough to fix by modifying/removing the accept() method.

Answer 1

Please take a look at what that example is for: In the JavaDoc comment you can read

/**
 * Example written by Bruno Lowagie in answer to:
 * http://stackoverflow.com/questions/24506830/can-we-use-text-extraction-strategy-after-applying-location-extraction-strategy
 */

and that stack overflow question starts with

I used the following code to get data in PDF from a particular location. I want to get bold text present in that location

When you wonder, therefore,

Why is there a need to specify a Rectangle?

the answer is: because the example is about finding bold text in a particular location.

You mention your forms were dynamic before flattening and fields don't have fixed positions. Thus, this filter probably is not optimal for your use case.

How can I change the flow so that I can perhaps just search for the question and then get the text right after it

In that case simply don't filter at all but use a plain LocationTextExtractionStrategy to extract text, search for the question text in the extracted text, and use the text thereafter up to the next question text.

Alternatively, if you still have the unflattened dynamic forms, you may consider extracting the xfa xml and extract the filled-in data from that xml.