Let me clarify again my use case and my solution so far:
I want to remove all files listed in the attachment list when I view the
pdf file with a pdf viewer. I encountered two different types of
attachments, embedded files located at document level, and file annotations
located on pages.
I started with removing the file annotations by using
"pPage->DeleteAnnotation( a );". That removed the attachment from the
viewers attachment list and from the page, but consulting the pdf file size
I recognized there's still the files data hidden inside the pdf. So I took
some File Annotation extraction code and bluntly added various Clear()
calls. That decreased the pdf file size roughly by the size of the removed
File Annotations. I did the same for embedded files, took some extraction
code and added Clear() calls, taking care that both attachment reference
and actual data is removed.
My question concerning the completeness / correctness of my removal code:
It seems my request was ambiguous. I originally only wanted to know whether
I missed some objects to be removed (for the given place) and if it's safe
to just call clear() on objects and dictionaries. I didn't know that there
might be more potential places for embedded attachments, which my removal
code cannot handle. If it just ignores this places, that shoulb be ok and
recognizable, if my code only deletes reference and leaves the filestreams,
that would be worse. I'll try to handle it later on. Do you have some
example pdf files where my removal code should fail in a way?
Best regards,
F.E.
2017-06-19 18:14 GMT+02:00 Leonard Rosenthol <lrose...@adobe.com>:
> As far as PDF 1.7 (ISO 32000-1) is concerned, that will handle both of the
> defined locations for embedded files – though not necessary other places
> that embedded filestreams can be used.
>
>
>
> For PDF 2.0 (ISO 32000-2), there are many more potential places that
> embedded file streams can exist.
>
>
>
> Leonard
>
>
>
> *From: *"F. E." <exler7...@gmail.com>
> *Date: *Sunday, June 18, 2017 at 12:51 PM
> *To: *"podofo-users@lists.sourceforge.net" <podofo-users@lists.
> sourceforge.net>
> *Subject: *[Podofo-users] Removing Embedded Attachments and File
> Annotations
>
>
>
> Hello Podofo Users,
>
> I'm using Podofo for removing Embedded Files and File Annotation. My code
> works fine so far, no files can be seen using a PDF Viewer, and I even
> managed to remove the dependent filestreams (otherwise files are still
> "hidden" inside the pdf and take space).
> What I'm not sure about is, whether my removal code is complete (removing
> all data) and safe (e.g. no double frees). So I'd like to commit my code
> here and ask whether you think the code is correct.
>
> On removing Embedded Files:
>
> There's code somewhere on how to extract embedded files. I refactored this
> code and added Clear instructions whenever I thought them necessary for the
> task.
>
>
> // Check if given ptr is a reference, if so, resolve ptr reference and
> store previous ptr to ref_ptr
> template <typename T>
> void CheckReference( const PdfMemDocument* doc, T* &ptr, T* &ref_ptr )
> {
> if ( IS_NULL( ptr ) || !ptr->IsReference() ) { return; }
>
> ref_ptr = ptr;
> ptr = doc->GetObjects().GetObject( ref_ptr->GetReference() );
> }
>
> template <typename T>
> void Clear( T* ptr )
> {
> if ( ptr ) { ptr->Clear(); }
> }
>
> void RemoveEmbeddedFileData( PdfObject *pObj ) const
> {
> PdfObject *pRefObj = NULL;
> CheckReference( m_pDocument, pObj, pRefObj );
>
> if ( !IS_NULL( pObj ) && pObj->GetDataType() ==
> ePdfDataType_Dictionary )
> {
> PdfDictionary &outerDict = pObj->GetDictionary();
> if ( outerDict.HasKey("EF") )
> {
> PdfDictionary &innerDict = outerDict.GetKey("EF")->
> GetDictionary();
> if ( innerDict.HasKey("F") )
> {
> PdfObject *pStreamObj = innerDict.GetKey("F"),
> *pStreamRefObj = NULL;
> CheckReference( m_pDocument, pStreamObj, pStreamRefObj
> );
> Clear( pStreamObj );
> Clear( pStreamRefObj );
> }
> innerDict.Clear();
> }
> outerDict.Clear();
> }
>
> Clear( pObj );
> Clear( pRefObj );
> }
>
> void RemoveEmbeddedFiles()
> {
> PdfObject *pEmbFilesObj = NULL;
> {
> const PdfNamesTree *pNamesTree = m_pDocument->GetNamesTree(
> true );
> RETURN_ON_NULL( pNamesTree );
>
> const PdfObject *pNamesTreeObj = pNamesTree->GetObject();
> RETURN_ON_NULL( pNamesTreeObj );
>
> pEmbFilesObj = pNamesTreeObj->GetIndirectKey("EmbeddedFiles");
> RETURN_ON_NULL( pEmbFilesObj );
> }
>
> PdfObject *pEmbFilesRefObj = NULL;
> CheckReference( m_pDocument, pEmbFilesObj, pEmbFilesRefObj );
> RETURN_ON_NULL( pEmbFilesObj );
>
> PdfObject *pEmbFilesNamesObj = pEmbFilesObj->GetIndirectKey("
> Names");
> RETURN_ON_NULL( pEmbFilesNamesObj );
>
> PdfArray* pEmbFilesNamesArray = &pEmbFilesNamesObj->GetArray();
> PdfArray::iterator it = pEmbFilesNamesArray->begin(), it_end =
> pEmbFilesNamesArray->end();
> for (; it != it_end; ++it ) { RemoveEmbeddedFileData( &(*it) ); }
>
> Clear( pEmbFilesNamesArray );
> Clear( pEmbFilesNamesObj );
>
> // Removing 'EmbeddedFiles' object seems not to be required!
> //Clear( pEmbFilesObj );
> //Clear( pEmbFilesRefObj );
> }
>
>
> On removing File Annotation Data:
>
> bool HasFileStream( const PdfDictionary &dict )
> {
> return dict.HasKey("EF") && dict.GetKey("EF")->
> GetDictionary().HasKey("F");
> }
>
> PdfObject* GetFileStream( PdfDictionary &dict )
> {
> return ( HasFileStream( dict ) ?
> dict.GetKey("EF")->GetDictionary().GetKey("F")
> : NULL );
> }
>
> void RemoveFileAttachment
> (
> const PdfMemDocument *pDoc,
> const PdfAnnotation *pAnnot
> )
> {
> if ( IS_NULL( pAnnot ) || !pAnnot->HasFileAttachement() ) {
> return; }
>
> PdfFileSpec *pFileSpec = pAnnot->GetFileAttachement();
> RETURN_ON_NULL( pFileSpec );
>
> PdfObject *pFileSpecObj = pFileSpec->GetObject();
> if ( IS_NULL( pFileSpecObj ) || pFileSpecObj->GetDataType() !=
> ePdfDataType_Dictionary ) { return; }
>
> PdfDictionary &fileDict = pFileSpecObj->GetDictionary();
> PdfObject *pFileStreamObj = GetFileStream( fileDict ),
> *pFileStreamRefObj = NULL;
> CheckReference( pDoc, pFileStreamObj, pFileStreamRefObj );
> RETURN_ON_NULL( pFileStreamObj );
>
> Clear( pFileStreamObj );
> Clear( pFileStreamRefObj );
> fileDict.Clear();
> Clear( pFileSpecObj );
> }
>
> void RemoveAnnotationsImpl
> (
> const PdfMemDocument *pDoc
> )
> {
> int pageCount = pDoc->GetPageCount();
> for ( int p = 0; p < pageCount; ++p )
> {
> PdfPage* pPage = pDoc->GetPage( p );
> CONTINUE_ON_NULL( pPage );
>
> int annotCount = pPage->GetNumAnnots();
> for ( int a = annotCount - 1; a >= 0; --a )
> {
> const PdfAnnotation* pAnnot = pPage->GetAnnotation( a );
> if ( IS_NULL( pAnnot ) || pAnnot->GetType() !=
> ePdfAnnotation_FileAttachement ) { continue; }
>
> RemoveFileAttachment( pDoc, pAnnot );
> pPage->DeleteAnnotation( a );
> }
> }
> }
>
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