[jira] [Created] (PDFBOX-2666) LayerUtility.wrapInSaveRestore creates invalid content if additional page content has been added in same session

["Michael Klink (JIRA)" <ji...@apache.org>]

Michael Klink created PDFBOX-2666:
-------------------------------------

             Summary: LayerUtility.wrapInSaveRestore creates invalid content if additional page content has been added in same session
                 Key: PDFBOX-2666
                 URL: https://issues.apache.org/jira/browse/PDFBOX-2666
             Project: PDFBox
          Issue Type: Bug
          Components: Utilities
    Affects Versions: 1.8.8
            Reporter: Michael Klink


The {{LayerUtility}} method {{wrapInSaveRestore}} creates an invalid page *Contents* entry if applied to a {{PDPage}} to which right before an additional {{PDPageContentStream}} has been added.

E.g.
{code}
PDDocument destinationPdfDoc = PDDocument.load(PDF_DEST);
PDDocument externalPdf = PDDocument.load(PDF_LAYER_SOURCE);

List<PDPage> destinationPages = destinationPdfDoc.getDocumentCatalog().getAllPages();
PDPage destPage = destinationPages.get(0);

// add additional content stream
PDPageContentStream additionalStream = new PDPageContentStream(destinationPdfDoc, destPage, true, false, true);
additionalStream.moveTo(100, 100);
additionalStream.lineTo(200, 200);
additionalStream.stroke();
additionalStream.close();

LayerUtility layerUtility = new LayerUtility(destinationPdfDoc);
PDXObjectForm firstForm = layerUtility.importPageAsForm(externalPdf, 0);
AffineTransform affineTransform = new AffineTransform();

// call wrapInSaveRestore
layerUtility.wrapInSaveRestore(destPage);

layerUtility.appendFormAsLayer(destPage, firstForm, affineTransform, "external page");

destinationPdfDoc.save(PDF_RESULT);
destinationPdfDoc.close();
externalPdf.close();
{code}

The resulting PDF contains a page like this:

{noformat}
5 0 obj
<<
/Type /Page
/Contents 8 0 R
/Resources 9 0 R
/MediaBox [0 0 595.2756 841.8898]
/Parent 2 0 R
>>  
8 0 obj
[10 0 R 11 0 R 12 0 R 13 0 R]
endobj 
11 0 obj
[19 0 R 20 0 R 21 0 R]
endobj 
{noformat}

But *Contents* may only contain either a stream or an array of streams, but not an array of streams and arrays.

This issue is due to {{LayerUtility.wrapInSaveRestore}} testing whether the *Contents* value is a stream or an array by 

{code}
if (contents instanceof COSStream)
{
    ...
}
else if( contents instanceof COSArray )
{
    ...
{code}

but {{new PDPageContentStream(destinationPdfDoc, destPage, true, false, true)}} sets the *Contents* to

{code}
compoundStream = new COSStreamArray(newArray);
...
sourcePage.setContents(new PDStream(compoundStream));
{code}

Thus, the *Contents* value is a {{COSStreamArray}} (which extends {{COSStream}}) instance which {{LayerUtility.wrapInSaveRestore}} recognizes as a stream but which actually represents an array of streams.



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