Tagged PDF: Adding Alt to the Structure Tree

AddAltTags Java

/*
    This file is part of the iText (R) project.
    Copyright (c) 1998-2023 Apryse Group NV
    Authors: Apryse Software.

    For more information, please contact iText Software at this address:
    sales@itextpdf.com
 */
package com.itextpdf.samples.sandbox.tagging;

import com.itextpdf.kernel.pdf.PdfArray;
import com.itextpdf.kernel.pdf.PdfDictionary;
import com.itextpdf.kernel.pdf.PdfDocument;
import com.itextpdf.kernel.pdf.PdfName;
import com.itextpdf.kernel.pdf.PdfReader;
import com.itextpdf.kernel.pdf.PdfString;
import com.itextpdf.kernel.pdf.PdfWriter;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

public class AddAltTags {
    public static final String DEST = "./target/sandbox/tagging/add_alt_tags.pdf";

    public static final String SRC = "./src/main/resources/pdfs/no_alt_attribute.pdf";

    public static void main(String[] args) throws Exception {
        File file = new File(DEST);
        file.getParentFile().mkdirs();

        new AddAltTags().manipulatePdf(DEST);
    }

    public void manipulatePdf(String dest) throws IOException {
        PdfDocument pdfDoc = new PdfDocument(new PdfReader(SRC), new PdfWriter(dest));
        PdfDictionary catalog = pdfDoc.getCatalog().getPdfObject();

        // Gets the root dictionary
        PdfDictionary structTreeRoot = catalog.getAsDictionary(PdfName.StructTreeRoot);
        manipulate(structTreeRoot);

        pdfDoc.close();
    }

    public void manipulate(PdfDictionary element) {
        if (element == null) {
            return;
        }

        // If an element is a figure, adds an /Alt entry.
        if (PdfName.Figure.equals(element.get(PdfName.S))) {
            element.put(PdfName.Alt, new PdfString("Figure without an Alt description"));
        }

        PdfArray kids = element.getAsArray(PdfName.K);

        if (kids == null) {
            return;
        }

        // Loops over all the kids
        for (int i = 0; i < kids.size(); i++) {
            manipulate(kids.getAsDictionary(i));
        }
    }
}

AddAltTags C#

using System;
using System.IO;
using iText.Kernel.Pdf;

namespace iText.Samples.Sandbox.Tagging
{
    public class AddAltTags
    {
        public static readonly string DEST = "results/sandbox/tagging/add_alt_tags.pdf";

        public static readonly String SRC = "../../../resources/pdfs/no_alt_attribute.pdf";

        public static void Main(String[] args)
        {
            FileInfo file = new FileInfo(DEST);
            file.Directory.Create();

            new AddAltTags().ManipulatePdf(DEST);
        }

        private void ManipulatePdf(String dest)
        {
            PdfDocument pdfDoc = new PdfDocument(new PdfReader(SRC), new PdfWriter(dest));
            PdfDictionary catalog = pdfDoc.GetCatalog().GetPdfObject();

            // Gets the root dictionary
            PdfDictionary structTreeRoot = catalog.GetAsDictionary(PdfName.StructTreeRoot);
            Manipulate(structTreeRoot);

            pdfDoc.Close();
        }

        private void Manipulate(PdfDictionary element)
        {
            if (element == null)
            {
                return;
            }

            // If an element is a figure, adds an /Alt entry.
            if (PdfName.Figure.Equals(element.Get(PdfName.S)))
            {
                element.Put(PdfName.Alt, new PdfString("Figure without an Alt description"));
            }

            PdfArray kids = element.GetAsArray(PdfName.K);

            if (kids == null)
            {
                return;
            }

            // Loops over all the kids
            for (int i = 0; i < kids.Size(); i++)
            {
                Manipulate(kids.GetAsDictionary(i));
            }
        }
    }
}