Dart

PDF Signature Appearance Text Substitution Keywords

See more PDF Signatures Examples

This example demonstrates the text substitution keywords that can be used in the PDF signature's appearance text.

Note: This example requires Chilkat v9.5.0.85 or greater.

Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // This example requires the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  final pdf = CkPdf();

  // Load a PDF to be signed.
  try {
    pdf.loadFile('qa_data/pdf/empty.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Options for signing are specified in JSON.
  final json = CkJsonObject();

  // In most cases, the signingCertificateV2 and signingTime attributes are required.
  json.updateInt('signingCertificateV2', 1);
  json.updateInt('signingTime', 1);

  // Put the signature on page 1, top left
  json.updateInt('page', 1);
  json.updateString('appearance.y', 'top');
  json.updateString('appearance.x', 'left');

  // Use a font scale of 7.0
  json.updateString('appearance.fontScale', '7.0');

  // The appearance of the PDF signature can contain any number of text lines.
  // Chilkat has defined a number of special keywords that can be used in any text line.
  // Each keyword is replaced with the actual value.
  // For example, "cert_cn" is replaced with the certificate subject's common name (CN).

  // Here we are creating a signature with many lines of text, to demonstrate each
  // keyword.
  json.updateString('appearance.text[0]', 'Date/time in PDF format: current_dt');
  json.updateString('appearance.text[1]', 'Current Local date/time: current_datetime');
  json.updateString('appearance.text[2]', 'GMT Timestamp: current_timestamp_gmt');
  json.updateString('appearance.text[3]', 'Local Timestamp: current_timestamp_local');
  json.updateString('appearance.text[4]', 'GMT RFC822 date/time: current_rfc822_dt_gmt');
  json.updateString('appearance.text[5]', 'Local RFC822 date/time: current_rfc822_dt_local');
  json.updateString('appearance.text[6]', 'Cert DN (Distinguished Name): cert_dn');
  json.updateString('appearance.text[7]', 'Cert Common Name: cert_cn');
  json.updateString('appearance.text[8]', 'Cert Organizational ID (2.5.4.97): cert_org_id');
  json.updateString('appearance.text[9]', 'Cert Email: cert_email');
  json.updateString('appearance.text[10]', 'Cert Organization: cert_organization');
  json.updateString('appearance.text[11]', 'Cert Organziational Unit: cert_ou');
  json.updateString('appearance.text[12]', 'Cert State: cert_state');
  json.updateString('appearance.text[13]', 'Cert Country: cert_country');
  json.updateString('appearance.text[14]', 'Cert Locality: cert_locality');
  json.updateString('appearance.text[15]', 'Cert Serial Number (hex): cert_serial_hex');
  json.updateString('appearance.text[16]', 'Cert Serial Number (decimal): cert_serial_dec');
  json.updateString('appearance.text[17]', 'Cert Thumbprint: cert_thumbprint');
  json.updateString('appearance.text[18]', 'Cert Issuer Common Name: cert_issuer_cn');

  final jpgData = CkBinData();
  try {
    jpgData.loadFile('qa_data/jpg/seal1.jpg');
  } on ChilkatException {
    print('Failed to load the JPG image.');
    return;
  }

  try {
    pdf.setSignatureJpeg(jpgData);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Specify that we want to display the JPG image in the center with 33% opacity.
  json.updateString('appearance.image', 'custom-jpg');
  json.updateString('appearance.imagePlacement', 'center');
  json.updateString('appearance.imageOpacity', '33');

  // Load the signing certificate. (Use your own certificate.)
  final cert = CkCert();
  try {
    cert.loadPfxFile('qa_data/pfx/myPdfSigningCert.pfx', 'pfx_password');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Tell the pdf object to use the certificate for signing.
  try {
    pdf.setSigningCert(cert);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  try {
    pdf.signPdf(json, 'qa_output/hello_signed.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('The PDF has been successfully cryptographically signed.');

  // The appearance of the signature appears in Adobe Acrobat as shown here:

  // (image:https://example-code.com/images/pdf_signature_text_replacements.jpg/endImage)
}