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Topic: Need help on Zlib
Conf: (P-PDF) Developers, Msg: 51055
From: skajan
Date: 5/29/2002 04:42 PM

Hi Genies

I have met a deadlock in my project because i am trying to use zlib.
Actually what i am trying to do is replace a text in the pdf which is using
Flate decode. I am explaining here in detail.

a) what we are doing in order to replace the text?

1) Extract the data between stream/endstream
2) Decompress it in memory
3) Search for "Shan Kajendran" in memory block
4) Replace it with "Leonard Rosenthol"
5) Compress the memory block using zlib
6) Put that compressed data back between the stream/endstream
7) Update /Length
8) Update the Xref table


b)what is the outcome ?
Blank pdf

c) what i have noticed ?

Zlib compressed pattern is different. The first character is starting
with 'x'.
Where all PDF files containing streams that have been encoded by Flate
starts with ASCII CODE 72 (H)
and followed by ASCII CODE 137 (PERTHOUSAND) character.Is this some kind
of BOD marker ?
If that's the case how do we incorporate this into the compressed stream
?
(Please see attached text file which decompressed and compressed the same
content stream without any modifications.)

b) Is compressed data (using zlib) should have the same pattern as PDF?

c) What settings we have to do?

At present i am doing as follows ( Thanks Leonard & Aandi)

deflateInit() to start, deflate() for each chunk of data
(with Z_NO_FLUSH set), and then deflateEnd() when we are done.


I am glad to send you the test code if someone ready to help me to pointout
where i am making mistake.


Thanks in advance
Shan Kajendran


(File attachment removed)

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