Inspect digital signatures

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31st May 2016

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    This file is part of the iText (R) project.
    Copyright (c) 1998-2016 iText Group NV


 * Example written by Bruno Lowagie in answer to:

import com.itextpdf.forms.PdfAcroForm;
import com.itextpdf.forms.fields.PdfFormField;
import com.itextpdf.kernel.pdf.*;
import com.itextpdf.test.annotations.type.SampleTest;

import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;
import org.junit.experimental.categories.Category;

import java.util.Map;

public class GetN2fromSig {
    public static String SRC = "./src/test/resources/pdfs/signature_n2.pdf";
    public static String CMP_RESULT = "BT\n" +
            "1 0 0 1 0 49.55 Tm\n" +
            "/F1 12 Tf\n" +
            "(This document was signed by Bruno)Tj\n" +
            "1 0 0 1 0 31.55 Tm\n" +
            "(Specimen.)Tj\n" +

    protected static String RESULT;

    public void before() throws Exception {
        PdfDocument pdfDoc = new PdfDocument(new PdfReader(SRC));

        PdfAcroForm form = PdfAcroForm.getAcroForm(pdfDoc, true);
        Map fields = form.getFormFields();

        PdfFormField field = fields.get("Signature1");
        PdfDictionary widget = field.getWidgets().get(0).getPdfObject();
        PdfDictionary ap = widget.getAsDictionary(PdfName.AP);
        PdfStream normal = ap.getAsStream(PdfName.N);
        PdfDictionary resources = normal.getAsDictionary(PdfName.Resources);
        PdfDictionary xobject = resources.getAsDictionary(PdfName.XObject);
        PdfStream frm = xobject.getAsStream(new PdfName("FRM"));
        PdfDictionary res = frm.getAsDictionary(PdfName.Resources);
        PdfDictionary xobj = res.getAsDictionary(PdfName.XObject);
        PdfStream n2 = xobj.getAsStream(new PdfName("n2"));
        byte[] stream = n2.getBytes();
        RESULT = new String(stream);

    public void compareResults() throws IOException {
        Assert.assertEquals(CMP_RESULT.trim(), RESULT.trim());



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