PDFBox - Coordinate System

Question

I would like to accomplish the following thing. I have a set of PDF files, first I would like to check the origin of the coordinate system. If the origin of the coordinate system for the pdf is not upper left [usually the origin is lower left], I would like to create a resultant PDF with coordinates on the upper left. I am trying to do this using PDFBox [the code snippet is below], however the resultant PDF is coming blank, what I am I doing wrong. I am new to PDFBox, hence any help in this regard is greatly appreciated.

        // loading the existing doc             
        PDDocument doc = PDDocument.load("C:\\Users\\test\\workspace\\example1.pdf");  
        List allPages = doc.getDocumentCatalog().getAllPages();  
        PDPageContentStream contentStream = null;  

        for( int i=0; i<allPages.size(); i++ )  
        {  
            PDPage page = (PDPage)allPages.get( i );  
            contentStream = new PDPageContentStream(doc, page);  
             contentStream.concatenate2CTM(1f, 0f, 0f, -1f, 0f,   page.findMediaBox().getHeight());  
             contentStream.saveGraphicsState();  
            contentStream.close();  

        }  
        doc.save("C:\\Users\\test\\workspace\\example2.pdf");  
        doc.close();  

Answer 1

You're creating an empty, transformed, content stream.

You need to get the existing content via page.getContents(), and wrap that in your transformation. Something like:

contentStream.conactenate2CTM(...);
contentStream.magicFunctionThatSucksUpTheExistingPageContent( page.getContents() );
contentStream.close();

PS: a call to saveGraphicsState() without a corresponding call to restoreGraphicsState() is a no-no.

Oh and it looks like "magicFunction..." is called appendRawCommands().