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Topic: Problems using zlib library for Flate encoding
Conf: (P-PDF) Developers, Msg: 129376
Date: 3/15/2005 08:22 AM
I'm trying to decode a PDF stream that uses a Flate filter. I'm attempting to use the open source zlib library to do so.(http://www.gzip.org/zlib/)
From reading other posts, it seems that some people have had success with this. Unfortunately, I have not yet gotten the desired results.
While the inflate() method does not return any errors, the decompressed data does not appear to be correct. I am trying to decompress a cross-reference stream to find the root (document catalog) offset. The decompressed data indicates that the document catalog is a freed object, but of course this would make for a corrupted document, which it is not.
I noticed that the zlib library does not have any clear means to input the parameters specified by the PDF file (predictor, columns, etc.). I'm suspicious that this is part of the problem, but I don't know how to get around it. Right now, I am simply using the default init_inflate() and inflate() methods.
If anyone has any suggestions, or any knowledge as to how the PDF Flate parameters correspond to the zlib library, I would greatly appreicate it.