LZW
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| + | |released=1984 | ||
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| + | '''LZW''' (Lempel-Ziv-Welch) is a lossless compression algorithm based on [[LZ78]]. It was developed by Terry Welch in 1984. It is infamous for being widely used in various standard formats (especially [[GIF]]) by developers unaware that it was encumbered by [[patents]]. The patents expired around 2003. | ||
| − | + | There are many variations of LZW in use. In general, LZW compresses a stream of ''symbols'' into a stream of bits. For general-purpose file compression, the symbols are usually taken to be bytes, but for GIF format the symbols are pixels. | |
| − | == | + | == Related formats == |
| + | * [[GIF]] | ||
| + | * [[TIFF]] | ||
| + | * [[compress (Unix)]] | ||
| + | * [[LZMW]] | ||
| + | |||
| + | == Resources == | ||
* [http://www.cs.duke.edu/courses/spring03/cps296.5/papers/welch_1984_technique_for.pdf A Technique for High-Performance Data Compression] Welch, Terry A. Computer, Vol. 17, No. 6 (June 1984): pp. 8-19 | * [http://www.cs.duke.edu/courses/spring03/cps296.5/papers/welch_1984_technique_for.pdf A Technique for High-Performance Data Compression] Welch, Terry A. Computer, Vol. 17, No. 6 (June 1984): pp. 8-19 | ||
* [http://en.wikipedia.org/wiki/LZW Lempel-Ziv-Welch : Wikipedia] | * [http://en.wikipedia.org/wiki/LZW Lempel-Ziv-Welch : Wikipedia] | ||
| − | |||
* [http://marknelson.us/2011/11/08/lzw-revisited/ LZW Revisited] a 2011 update to an article by Mark Nelson written 20 years earlier. | * [http://marknelson.us/2011/11/08/lzw-revisited/ LZW Revisited] a 2011 update to an article by Mark Nelson written 20 years earlier. | ||
| − | * [http://www.fileformat.info/mirror/egff/ch09_04.htm Lempel-Ziv-Welch (LZW) Compression] | + | * [http://www.fileformat.info/mirror/egff/ch09_04.htm Lempel-Ziv-Welch (LZW) Compression], from the [[Encyclopedia of Graphics File Formats]] |
| + | * [http://www.infinitepartitions.com/cgi-bin/showarticle.cgi?article=art010 How LZW (GIF) Compression Works] | ||
| + | * [http://www.google.com/patents/US4558302 US Patent 4,558,302] | ||
Latest revision as of 14:25, 16 October 2020
LZW (Lempel-Ziv-Welch) is a lossless compression algorithm based on LZ78. It was developed by Terry Welch in 1984. It is infamous for being widely used in various standard formats (especially GIF) by developers unaware that it was encumbered by patents. The patents expired around 2003.
There are many variations of LZW in use. In general, LZW compresses a stream of symbols into a stream of bits. For general-purpose file compression, the symbols are usually taken to be bytes, but for GIF format the symbols are pixels.
[edit] Related formats
[edit] Resources
- A Technique for High-Performance Data Compression Welch, Terry A. Computer, Vol. 17, No. 6 (June 1984): pp. 8-19
- Lempel-Ziv-Welch : Wikipedia
- LZW Revisited a 2011 update to an article by Mark Nelson written 20 years earlier.
- Lempel-Ziv-Welch (LZW) Compression, from the Encyclopedia of Graphics File Formats
- How LZW (GIF) Compression Works
- US Patent 4,558,302
