Dart Requires Chilkat v11.7.0+

Remove PDF Objects Nothing Refers To

See more PDF Optimization Examples

Demonstrates removeUnreferenced. When a page, an image or a whole section is replaced in an editor, the objects it used often stay in the file with nothing pointing at them any more. They are not old revisions -- they are in the current revision, simply unreachable -- so only a reachability walk from the document catalog finds them. In a publication assembled over several editing passes this is frequently the largest single saving. 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 watersense_accomplishments.pdf

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

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

  print('fileSize: ${jsonOut.intOf('fileSize')}');
  print('removeUnreferenced would save: ${jsonOut.intOf('estimatedSavings.removeUnreferenced')}');

  // Optimize with the defaults and see how many objects were actually dropped.
  try {
    pdf.optimize('optimize', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

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

  print('objects removed: ${jsonOut.intOf('actions.removeUnreferenced.count')}');
  print('bytes saved:     ${jsonOut.intOf('actions.removeUnreferenced.bytesSaved')}');

  // Nothing a page needs is ever removed: the walk starts at the document catalog and follows every
  // reference, including the ones in annotations, the structure tree, named destinations and the
  // optional-content configuration.
  print('pages after: ${pdf.numPages}');
}