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data compression

Hello,

Anyone could help me?
Where can I find a good data compression library, or better, how can I
write my own?

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Re:data compression


Writing your own in an excellent exercise. Huffman coding is a sensible
start, but it doesn't offer particularly good compression ratios. Try
searching the net for the LZ or LZW compression algorithms.

MH.

Quote
fab...@martinus.com.br wrote:

> Hello,

> Anyone could help me?
> Where can I find a good data compression library, or better, how can I
> write my own?

> --== Sent via Deja.com http://www.deja.com/ ==--
> ---Share what you know. Learn what you don't.---

--
Martin Harvey.
mar...@aziraphale.demon.co.uk
mc...@harvey27.demon.co.uk
http://www.harvey27.demon.co.uk/mch24/
EFFNet: Diaspar-
ICQ: 37298917

Jesus replied: "I am the way, the truth, and the life;
no one comes to the Father, except by me."
(John 14:6).

Re:data compression


There are a few commercial/shareware and freeware ones I am aware of.

Commercial/shareware
Abbrevia, from http://www.turbopower.com
VCLZip, http://ourworld.compuserve.com/homepages/boylank
XCeed, http://www.xceedsoft.com

Freeware
ZLib ported to pascal, http://www.tu-chemnitz.de/~nomssi/
Delphi Zip, http://www-afsc.saia.af.mil/~englere/

You can also search the data compression section at http://www.torry.ru

Best regards,

Michel
------
http://www.cam.org/~mibra/spider
Envision Image Library
Spider Object Database
Spider Container and Persistent Classes  (freeware)
WordShare string localization  (freeware)

Quote
fab...@martinus.com.br wrote:

> Hello,

> Anyone could help me?
> Where can I find a good data compression library, or better, how can I
> write my own?

> --== Sent via Deja.com http://www.deja.com/ ==--
> ---Share what you know. Learn what you don't.---

Re:data compression


Writing compression algorithms is a big task.
I have tried to figure out how to build the Huffman tree, but failed.
The LZ77 and LZW algorithms are much easier to understand. The hash search
algorithm in LZW is patented though. You can do without it, I think, but
the compression will be slower.

My own choice has been to use ZLIB. It implements LZ77 followed by a
Huffman encoding.
The result is much like PKZIP's deflate methode, but with ZLIB it seems
you need to do a good deal of coding in order to create/decompress
standard ZIP files.
(I simply used ZLIB as it was and fairly quickly had something up and
running.)

J.Hansen

Quote
fab...@martinus.com.br wrote:
> Hello,

> Anyone could help me?
> Where can I find a good data compression library, or better, how can I
> write my own?

> --== Sent via Deja.com http://www.deja.com/ ==--
> ---Share what you know. Learn what you don't.---

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