JavaScript 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. JavaScript

var 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

var pdf = new CkPdf();
success = pdf.LoadFile("qa_data/pdf/watersense_accomplishments.pdf");
if (success == false) {
    console.log(pdf.LastErrorText);
    return;
}

var json = new CkJsonObject();
var jsonOut = new CkJsonObject();
success = pdf.Optimize("audit",json,jsonOut);
if (success == false) {
    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.
success = pdf.Optimize("optimize",json,jsonOut);
if (success == false) {
    console.log(pdf.LastErrorText);
    return;
}

success = pdf.WriteFile("qa_output/watersense_optimized.pdf");
if (success == false) {
    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);