Question

Is there an API available in iText library to detect whether the PDF file has compressed xref table?

PDFReader class of this library has some useful API with regards to xref, but none serve my purpose.

The requirement is to:

1. Check if the PDF has xref compressed table.
2. If 1 is true -> then “Uncompress” xref table.
3. Send the byte stream for further processing.
4. Once the processing completes “Compress” back the xref table to its original form

Any pointers in this regard would be appreciated.

P.S.: The implementation is not restricted to iText. Any other Java library which can achieve it can be used. Licencing (if required) is also not an issue.

Answer 1

As it turns out, this is already supported in iText.
You need to create a PdfReader instance and then use isNewXrefType().

To uncompress the XRef table of a PDF document, you can use this method:

public void uncompressXRef(String src, String dest)
    throws IOException, DocumentException {
    PdfReader reader = new PdfReader(src);
    PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(dest));
    stamper.close();
    reader.close();
}

To recompress the XRef table, use this method:

public void recompressXRef(String src, String dest)
    throws IOException, DocumentException {
    PdfReader reader = new PdfReader(src);
    PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(dest));
    stamper.getWriter().setFullCompression();
    stamper.close();
    reader.close();
}