PDFBox LayerUtility - Importing layers into existing PDF

Question

I am using pdfbox to manipulate PDF content. I have a big PDF file (say 500 pages). I also have a few other single page PDF files containing only a single image which are around 8-15kb per file at the max. What I need to do is to import these single page pdf's like an overlay onto certain pages of the big PDF file.

I have tried the LayerUtility of pdfbox where I've succeeded but it creates a very large sized file as the output. The source pdf is about 1MB before processing and when added with the smaller pdf files, the size goes upto 64MB. And sometimes I need to include two smaller PDF's onto the bigger one.

Is there a better way to do this or am I just doing this wrong? Posting code below trying to add two layers onto a single page:

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overlayDoc[pCounter] = PDDocument.load("data\\" + overlay + ".pdf");
outputPage[pCounter] = (PDPage) overlayDoc[pCounter].getDocumentCatalog().getAllPages().get(0);

LayerUtility lu = new LayerUtility( overlayDoc[pCounter] );
form[pCounter] = lu.importPageAsForm( bigPDFDoc, Integer.parseInt(pageNo)-1);
lu.appendFormAsLayer( outputPage[pCounter], form[pCounter], aTrans, "OVERLAY_"+pCounter );
outputDoc.addPage(outputPage[pCounter]);

mOverlayDoc[pCounter] = PDDocument.load("data\\" + overlay2 + ".pdf");                      
mOutputPage[pCounter] = (PDPage) mOverlayDoc[pCounter].getDocumentCatalog().getAllPages().get(0);

LayerUtility lu2 = new LayerUtility( mOverlayDoc[pCounter] );
mForm[pCounter] = lu2.importPageAsForm(outputDoc, outputDoc.getNumberOfPages()-1);
lu.appendFormAsLayer( mOutputPage[pCounter], mForm[pCounter], aTrans, "OVERLAY_2"+pCounter );

outputDoc.removePage(outputPage[pCounter]);
outputDoc.addPage(mOutputPage[pCounter]);
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Your code unfortunately is somewhat incomplete. It isn't apparent how you put other pages into the outputDoc. The pCounter variable seems to indicate that you do something similar to the above to every page, and in that case it is no surprise that the file size explodes because there are some deep copies involved that might just multiply shared resources. — mkl
Yes, pCounter is ideally the total no of pages. My only option was to use arrays because the above code runs in a loop and until outputDoc is saved, I need to store the data of every page somewhere separate or I run into COSVisitor exceptions. Is there a neater way of doing this? How can I limit the resouces? I cannot use the Overlay class since it does not have a facility to selectively overlay pages. Any help is appreciated! — Joey Ezekiel

mkl mkl · Accepted Answer · 2013-07-22T10:33:01

With code like the following I don't see any unepected growth of size:

PDDocument bigDocument = PDDocument.load(BIG_SOURCE_FILE);
LayerUtility layerUtility = new LayerUtility(bigDocument);
List bigPages = bigDocument.getDocumentCatalog().getAllPages();

// import each page to superimpose only once
PDDocument firstSuperDocument = PDDocument.load(FIRST_SUPER_FILE);
PDXObjectForm firstForm = layerUtility.importPageAsForm(firstSuperDocument, 0);

PDDocument secondSuperDocument = PDDocument.load(SECOND_SUPER_FILE);
PDXObjectForm secondForm = layerUtility.importPageAsForm(secondSuperDocument, 0);

// These things can easily be done in a loop, too
AffineTransform affineTransform = new AffineTransform(); // Identity... your requirements may differ
layerUtility.appendFormAsLayer((PDPage) bigPages.get(0), firstForm, affineTransform, "Superimposed0");
layerUtility.appendFormAsLayer((PDPage) bigPages.get(1), secondForm, affineTransform, "Superimposed1");
layerUtility.appendFormAsLayer((PDPage) bigPages.get(2), firstForm, affineTransform, "Superimposed2");

bigDocument.save(BIG_TARGET_FILE);

As you see I superimposed the first page of FIRST_SUPER_FILE on two pages of the target file but I only imported the page once. Thus, also the resources of that imported page are imported only once.

This approach is open for loops, too, but don't import the same page multiple times! Instead import all required template pages once up front as forms and in the later loop reference those forms again and again.

(I hope this solves your issue. If not, supply more code and the sample PDFs to reproduce your issue.)

PDFBox LayerUtility - Importing layers into existing PDF

1 Answers