React Native 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. React Native

import { JsonObject, Pdf } from '@chilkat/react-native'

function chilkatExample() {
  // 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

  const pdf = new Pdf();
  try {
    pdf.loadFile('qa_data/pdf/watersense_accomplishments.pdf');
  } catch {
    console.log(pdf.lastErrorText);
    return;
  }

  const json = new JsonObject();
  const jsonOut = new JsonObject();
  try {
    pdf.optimize('audit', json, jsonOut);
  } catch {
    console.log(pdf.lastErrorText);
    return;
  }

  console.log(`fileSize: ${jsonOut.intOf('fileSize')}`);
  console.log(`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);
  } catch {
    console.log(pdf.lastErrorText);
    return;
  }

  try {
    pdf.writeFile('qa_output/watersense_optimized.pdf');
  } catch {
    console.log(pdf.lastErrorText);
    return;
  }

  console.log(`objects removed: ${jsonOut.intOf('actions.removeUnreferenced.count')}`);
  console.log(`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.
  console.log(`pages after: ${pdf.numPages}`);
}