Dart Requires Chilkat v11.7.0+

Add an Image (Logo) Watermark to a PDF

See more PDF Watermark Examples

Demonstrates an image watermark placed in a corner of every page. The image is a PNG or JPEG given either by path ("image.path") or, as here, as base64 in the JSON itself ("image.base64"), which suits a server that keeps its logo in a database rather than on disk. PNG transparency is kept. Giving only a width keeps the aspect ratio, and the units member says those numbers are inches rather than points. 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.

  // The PDF used in this example is available at four_pages.pdf

  final pdf = CkPdf();
  try {
    pdf.loadFile('qa_data/pdf/four_pages.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final json = CkJsonObject();
  json.updateString('type', 'image');

  // A small PNG logo, base64 encoded.  Use "image.path" instead to name a PNG or JPEG file:
  //    ignore = json.UpdateString("image.path","logo.png");
  json.updateString('image.base64', 'iVBORw0KGgoAAAANSUhEUgAAAGAAAAAgCAYAAADtwH1UAAAApElEQVR42u3a7QmAIBgAYTdpo/ZphhZti6IBylLrlXoO/G3cIeFHSgAAFDKM08rCy8Jzg6Ug8UJ0JF+EDuSXRGgxX8+jufxlTk0nFuCCiF360aidXICMiDP5uQgCXAxQI782ggAHEu7IP4sgQOcBIMA35ItgBQhQEqBmtbX6xl//hAUI3gcIELwTFiD4LEiA4NNQAYLvA+BGzJ0wvIrwLggA8DgbwPbrr8c7+lkAAAAASUVORK5CYII=');

  // The size to draw it at.  Give only the width and the height follows the aspect ratio.
  json.updateString('units', 'in');
  json.updateNumber('image.width', '1.5');

  // Bottom-right, half an inch in from the page edges.
  json.updateString('position.align', 'bottomRight');
  json.updateNumber('position.margin', '0.5');
  json.updateNumber('opacity', '0.85');
  json.updateString('id', 'logo');

  final jsonOut = CkJsonObject();
  try {
    pdf.watermark('add', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('id: ${jsonOut.stringOf('id')} pages: ${jsonOut.stringOf('pages')}');

  try {
    pdf.writeFile('qa_output/four_pages_logo.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Sample output:

  // id: logo pages: 1-4
}