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Question: Lemon trees are nice...  (Voting closed: June 04, 2002, 03:33:53 AM)
Yes - 6 (100%)
Total Voters: 6

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Author Topic: Does anybody know anything about compression?  (Read 8226 times)
Antoni Gual
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« Reply #15 on: January 30, 2003, 05:41:00 PM »

Just found a link to a series of articles on compression
http://www.rebolforces.com/articles/compression1.html
it seems interesting and well explained.
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Antoni
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« Reply #16 on: January 30, 2003, 06:47:24 PM »

png is based somewhat on zip compression right?  Anyways thats something to look up, loading up png, the whole format is open source and comes with libs ans stuff so i guess its a good start.

The reason i assume png uses some form of zip compression is becuase well, it needs zlib to run.

And i think zip is lzw right? and upx uses a slighltly different form of lzw.
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LooseCaboose
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« Reply #17 on: January 30, 2003, 08:49:26 PM »

Red_Marvin, your approach may actually work correctly if you try to create the mathmatical formula for blocks of data rather than the entire file. For example if a sequence of bytes in the file were a, b, c, d, e, f, g, ... Then you could create a formula for that block and store a block lookup table at the beginning of the compressed file.

The problem is that not all data can be represented by mathmatical formula, completely random data being the prime example and that it would be computationaly expensive for a compression algorithm to try and derive formulas from data, how would the machine know how big to make the blocks, or the best arrangement.

Most good compression algorithms (ie JPEG and bzip) are hybrids of several compression techniques. A good compression algorithm should also yield good results for most types of data, ie an algorithm that compresses some data very well, but makes random data larger is not ideal.
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