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Topic: Re: How to write a compression routine
Conf: (P-PDF) Developers, Msg: 57411
From: LeonardR
Date: 5/29/2002 05:25 PM

At 03:43 PM 8/28/2001 -0400, p-pdf-developer Listmanager wrote:
>Recently I have written a PDF conversion program which takes mainframe
>data reports and converts them to PDF files. So far it works pretty good.


>One thing I did want to add was compression. The compression is more for
>security purposes than for actual compression. This way people can't just
>read the PDF file as a text file and change numbers around.

Seems perfectly reasonable.

>I'm starting to write an LZW compression routine

Start by throwing this away QUICKLY before a large group of money
hungry lawyers show up at your door. LZW is a patented algorithm and the
folks at Unisys want a nice chunk of change for the license.

> From what I've seen you can just compress the stuff in between the STREAM
> and END STREAM statements.


>Do you treat each section in between as if it was a separate compressed


>What is FLATE?

It's another name for Zip - see .

>Is it possible or even allowed to write a FLATE compression routine, or do
>you have to have specific software? I don't want to use specific software
>because I want to run this on the mainframe.

zlib will happily compile on your mainframe.


Leonard Rosenthol
Director of Software Development (215) 922-3509 (voice)
Appligent, Inc. (formerly Digital Applications) (610) 284-4233 (fax)

PGP Fingerprint: 8CC9 8878 921E C627 0BC1 15BB FC19 64A9 0016 1397

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