Lazarus Pascal Requires Chilkat v11.7.0+

Remove a PDF's Old Revisions

See more PDF Optimization Examples

Demonstrates dropOldRevisions. A PDF that has been edited and saved several times carries every earlier revision: the superseded objects are still in the file, reachable through the older cross-reference sections. The audit reports them as "oldRevisions", and dropping them is often the single largest saving in a real document. Dropping them requires a full rewrite, which is why it invalidates existing digital signatures. Lazarus Pascal

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.FileAccess,
  Chilkat.Pdf,
  Chilkat.JsonObject;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  pdf: TPdf;
  json: TJsonObject;
  jsonOut: TJsonObject;
  fac: TFileAccess;

begin
  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 grand_canyon_hiking_guide.pdf

  pdf := TPdf.Create;
  success := pdf.LoadFile('qa_data/pdf/grand_canyon_hiking_guide.pdf');
  if (success = False) then
    begin
      WriteLn(pdf.LastErrorText);
      Exit;
    end;

  //  How much of this file is superseded revisions?
  json := TJsonObject.Create;
  jsonOut := TJsonObject.Create;
  success := pdf.Optimize('audit',json,jsonOut);
  if (success = False) then
    begin
      WriteLn(pdf.LastErrorText);
      Exit;
    end;

  WriteLn('fileSize:     ' + jsonOut.IntOf('fileSize'));
  WriteLn('oldRevisions: ' + jsonOut.IntOf('usage.oldRevisions.bytes'));

  //  Drop them, and nothing else, so that the saving is attributable.
  json.UpdateBool('compressUncompressed',False);
  json.UpdateBool('recompressFlate',False);
  json.UpdateBool('replaceLegacyFilters',False);
  json.UpdateBool('imagePredictors',False);
  json.UpdateBool('dedupeStreams',False);
  json.UpdateBool('dedupeObjects',False);
  json.UpdateBool('removeUnreferenced',False);
  json.UpdateBool('removeUnusedResources',False);
  json.UpdateBool('removeUnusedLayers',False);
  json.UpdateBool('coalesceContent',False);
  json.UpdateBool('tidyContent',False);
  json.UpdateBool('subsetFonts',False);
  json.UpdateBool('dropOldRevisions',True);

  success := pdf.Optimize('optimize',json,jsonOut);
  if (success = False) then
    begin
      WriteLn(pdf.LastErrorText);
      Exit;
    end;

  success := pdf.WriteFile('qa_output/grand_canyon_one_revision.pdf');
  if (success = False) then
    begin
      WriteLn(pdf.LastErrorText);
      Exit;
    end;

  //  The saving is an estimate: what the old revisions occupied is known exactly, but the writer
  //  decides the final layout.  Measure the written file for the real number.
  fac := TFileAccess.Create;
  WriteLn('bytesSaved (reported): ' + jsonOut.IntOf('bytesSaved'));
  WriteLn('written file:          ' + fac.FileSize('qa_output/grand_canyon_one_revision.pdf'));


  pdf.Free;
  json.Free;
  jsonOut.Free;
  fac.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.