Java 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. Java

import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    boolean success = false;

    //  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

    CkPdf pdf = new CkPdf();
    success = pdf.LoadFile("qa_data/pdf/watersense_accomplishments.pdf");
    if (success == false) {
        System.out.println(pdf.lastErrorText());
        return;
        }

    CkJsonObject json = new CkJsonObject();
    CkJsonObject jsonOut = new CkJsonObject();
    success = pdf.Optimize("audit",json,jsonOut);
    if (success == false) {
        System.out.println(pdf.lastErrorText());
        return;
        }

    System.out.println("fileSize: " + jsonOut.IntOf("fileSize"));
    System.out.println("removeUnreferenced would save: " + jsonOut.IntOf("estimatedSavings.removeUnreferenced"));

    //  Optimize with the defaults and see how many objects were actually dropped.
    success = pdf.Optimize("optimize",json,jsonOut);
    if (success == false) {
        System.out.println(pdf.lastErrorText());
        return;
        }

    success = pdf.WriteFile("qa_output/watersense_optimized.pdf");
    if (success == false) {
        System.out.println(pdf.lastErrorText());
        return;
        }

    System.out.println("objects removed: " + jsonOut.IntOf("actions.removeUnreferenced.count"));
    System.out.println("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.
    System.out.println("pages after: " + pdf.get_NumPages());
  }
}