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Topic: LZW

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	The GIF Controversy: A Software Developer's Perspective (lzw.info)
		LZW itself is a refinement of other algorithms published in the years before (Ziv-Lempel and others).
		The LZW patent, as well as its international counterparts, and similar patents filed by others, are expected to remain valid for at least 20 years from the original filing date of June 20, 1983, i.e.
		While the original article on LZW was published in 1984, the LZW patent issue first surfaced in the press in 1989, when the BTLZ algorithm (a procedure similar to LZW developed and patented by British Telecom) was to be approved for data compression into the V.42bis modem standard.
	www.cloanto.com /users/mcb/19950127giflzw.html (4892 words)

	Application Note about LZW Compression
		LZW (short for Lempel-Ziv-Welch) is a lossless compression technique that is an optional part of the GIF and TIFF image file formats.
		LZW compression is commonly used for 1- through 8-bit palette color images and less often for 24-bit RGB images.
		Notice that for the 24-bit image LZW (or run length encoding) is not really compressing but actually increasing the space requirements.
	www.catenary.com /appnotes/lzwcomp.html (638 words)

	LZW Compression - The Code Project - C++ / MFC
		But I will explain what is the dynamic and static compression in the LZW implementations, and some problems that someone might face during implementing LZW algorithm.
		The files LZWCompression.h, LZWCompression.cpp, Dictionary.h, Dictionary.cpp are all you need to use, to insert the LZW into your project.
		The class creates its own dictionary, and clears it after the use of the compression or decompression process, so using one class to manage all your LZW compression in the project is easy.
	www.codeproject.com /cpp/LZWCompression.asp (1342 words)

	LZW Data Compression at Mark Nelson
		The LZW compression algorithm in its simplest form is shown in Figure 1.
		One reason for the efficiency of the LZW algorithm is that it does not need to pass the string table to the decompression code.
		I wrote a LZW encoder in MatLab and the execution time is at least 100 times that of your code so you may have saved me months of execution time.
	marknelson.us /1989/10/01/lzw-data-compression (8377 words)

	file:///d:/³ÌÐò×ÊÁÏ/format2/lzwexp.txt
		lzw is a way of compressing data that takes advantage of repetition of strings in the data.
		lzw manipulates three objects in both compression and decompression: the charstream, the codestream, and the string table.
		also, note that "straight lzw" compression runs the risk of overflowing the string table - getting to a code which can't be represented in the number of bits you've set aside for codes.
	www.moon-soft.com /program/FORMAT/graphics/lzwexp.htm (2646 words)

	LZW Data Compression
		LZW is a data compression method that takes advantage of this repetition.
		LZW starts out with a dictionary of 256 characters (in the case of 8 bits) and uses those as the "standard" character set.
		Although LZW generally does not require a pseudo-eof (normally, it reads data until it can read no more), it is a good idea to use one.
	www.cs.duke.edu /csed/curious/compression/lzw.html (1296 words)

	Dr. Dobb's \| Replacing a Dictionary with a Square Root \| April 9, 2002
		For simplicity of analysis, the input alphabet is restricted to the letters "a" through "z," and the dictionary codes are represented by strings such as "(12)." In practice, GIF literal values and dictionary codes are represented by variable-length bit fields, a complexity that's moot for the purposes of this article.
		LZW happens to exploit the repeated is and si because of the particular behavior of its dictionary, as shown in the compress method.
		It prints the LZW encoding of the strings that are from 1 to 20 repetitions of the single character "a." Figure 1 is the output of generateCompressMapping (Listing Two).
	www.ddj.com /184404817 (1670 words)

	Lempel-Ziv-Welch (LZW)
		The LZW compression method is derived from LZ78 as introduced by Jacob Ziv and Abraham Lempel.
		The LZW method is covered by patents valid for a number of countries, e.g.
		LZW is an important part of a variety of data formats.
	www.binaryessence.com /dct/en000141.htm (182 words)

	LZW information - Search.com
		LZW (Lempel-Ziv-Welch) is a universal lossless data compression algorithm created by Abraham Lempel, Jacob Ziv, and Terry Welch.
		Two US patents were issued for the LZW algorithm: U.S. Patent 4,814,746 by Victor S. Miller and Mark N. Wegman and assigned to IBM, originally filed on June 1, 1983, and U.S. Patent 4,558,302 by Welch, assigned to Sperry Corporation, later Unisys Corporation, filed on June 20, 1983.
		Although the LZW acronym refers to the inventors as Lempel, Ziv and Welch, some people claim the intellectual property rights go to Ziv first, so the method must be called the Ziv-Lempel-Welch algorithm, and not the Lempel-Ziv-Welch algorithm.
	domainhelp.search.com /reference/LZW (714 words)

	[No title] (Site not responding. Last check: )
		LZW is an example of pattern-matching, and huffman and arithmetic encoding are both forms of prediction (they predict that the most frequently-used values will be used most often, and so assign such values shorter codes).
		LZW is simply a pattern-matching compressor, whereas zip deflate (for example) uses both pattern matching (an LZ77 variant), and value prediction (huffman).
		However, writing a better compressor than LZW (even if this is done simply by adding further stages of compression to the LZW algorithm, like huffman or arithmetic coding) is not hard.
	www.math.niu.edu /~rusin/known-math/00_incoming/lzw_huff (406 words)

	DataCompression.info - LZ78/LZW and derivatives (Site not responding. Last check: )
		This topic encompasses the LZ78 algorithm and its descendant, LZW.
		LZW is best know as the core compennt of the GIF compression format.
		A nice explanation of LZW compression from the fine folks at the Data Compression Center.
	datacompression.info /LZW.shtml (1249 words)

	LZW Data Compression (Site not responding. Last check: )
		A quick examination of the algorithm shows that LZW is always trying to output codes for strings that are already known.
		One reason for the efficiency of the LZW algorithm is that it does not need to pass the string table to the decompression code.
		LZW compression excels when confronted with data streams that have any type of repeated strings.
	www.eg.bucknell.edu /~cs350/S06/lzw.html (3965 words)

	LZW - Sonic Retro
		LZW (Lempel-Ziv-Welch) is a lossless data compression algorithm.
		Two US patents were issued for the LZW algorithm: US patent No. 4,814,746 by Victor S. Miller and Mark N. Wegman and assigned to IBM, originally filed on June 1, 1983, and US Patent No. 4,558,302 by Welch, assigned to Sperry Corporation, later Unisys Corporation, filed on June 20, 1983.
		Although the LZW acronym obviously refers to the inventors as Lempel, Ziv and Welch, some people claim the intellectual property rights go to Ziv first, so the method must be called the Ziv-Lempel-Welch algorithm, and not the Lempel-Ziv-Welch algorithm.
	info.sonicretro.org /LZW (871 words)

	The GIF Controversy: A Software Developer's Perspective (lzw.info)
		LZW itself is a refinement of other algorithms published in the years before (Ziv-Lempel and others).
		The LZW patent, as well as its international counterparts, and similar patents filed by others, are expected to remain valid for at least 20 years from the original filing date of June 20, 1983, i.e.
		While the original article on LZW was published in 1984, the LZW patent issue first surfaced in the press in 1989, when the BTLZ algorithm (a procedure similar to LZW developed and patented by British Telecom) was to be approved for data compression into the V.42bis modem standard.
	cloanto.com /users/mcb/19950127giflzw.html (4892 words)

	The LZW compression algorithm (Site not responding. Last check: )
		LZW is named after Abraham Lempel, Jakob Ziv and Terry Welch, the scientists who developed this compression algorithm.
		The code that the LZW algorithm outputs can be of any arbitrary length, but it must have more bits in it than a single character.
		This has seriously hampered the popularity of LZW compression and in the long run we will probably see it being replaced by less costly (read: free) algorithms.
	www.prepressure.com /techno/compressionlzw.htm (546 words)

	LZW Data Compression at Mark Nelson
		The LZW compression algorithm in its simplest form is shown in Figure 1.
		One reason for the efficiency of the LZW algorithm is that it does not need to pass the string table to the decompression code.
		I wrote a LZW encoder in MatLab and the execution time is at least 100 times that of your code so you may have saved me months of execution time.
	www.dogma.net /markn/articles/lzw/lzw.htm (6704 words)

	Lempel-Ziv-Welch (LZW) Compression (Site not responding. Last check: )
		LZW is a general compression algorithm capable of working on almost any type of data.
		LZW is referred to as a substitutional or dictionary-based encoding algorithm.
		LZW goes beyond most dictionary-based compressors in that it is not necessary to preserve the dictionary to decode the LZW data stream.
	netghost.narod.ru /gff/graphics/book/ch09_04.htm (3381 words)

	Lempel-Ziv-Welch (LZW) Encoding Discussion and Implementation
		Entries in the LZW dictionary are strings, and every LZW code word is a reference to a string in the dictionary.
		However, the LZW algorithm does not impose a limit on the length of strings that are encoded.
		Further discussion of LZW with links to other documentation and libraries may be found at http://www.datacompression.info/lzw.shtml.
	michael.dipperstein.com /lzw (4219 words)

	LZW compression - a definition from Whatis.com
		LZW compression is the compression of a file into a smaller file using a table-based lookup algorithm invented by Abraham Lempel, Jacob Ziv, and Terry Welch.
		LZW compression is also suitable for compressing text files.
		A particular LZW compression algorithm takes each input sequence of bits of a given length (for example, 12 bits) and creates an entry in a table (sometimes called a "dictionary" or "codebook") for that particular bit pattern, consisting of the pattern itself and a shorter code.
	whatis.techtarget.com /definition/0,,sid9_gci214337,00.html (259 words)

	NewsForge \| Bringing back LZW compression
		LZW has other more vital uses, chief among them being that it is the default compression algorithim for the Tagged Image File Format (TIFF) file format.
		Furthermore, they could also still supply a working LZW function separately, for those who needed it, which could be implemented with a single patch to the library.
		This is important because the current "LZW compression kit" (as it is referred to by libtiff) is a drop-in replacement built for only for libtiff 3.5.5 through the 3.6 series only.
	software.newsforge.com /software/05/06/23/2150233.shtml?tid=130 (1944 words)

	LZW coding algorithm
		LZW is a so-called commercial version of LZ78.
		The LZW algorithm uses the same principles and ideas as LZ78 does, while adding several technical improvements over LZ78.
		As it can be seen from the demonstrated examples of compression using LZ78 and LZW, these algorithms achieve maximal efficiency when the length of the input string is of infinitely long size.
	www.cs.technion.ac.il /Labs/Isl/Project/Projects_done/VisionClasses/DIP/Lossless_Compression/node18.html (634 words)

	[70] Introduction to data compression (long)
		The most well-known scheme (in fact the most well-known of all the Lempel-Ziv compressors, the one which is generally (and mistakenly) referred to as "Lempel-Ziv Compression"), is Terry Welch's LZW scheme, which he designed in 1984 for implementation in hardware for high- performance disk controllers.
		LZW decompression takes the stream of codes and uses it to exactly recreate the original input data.
		LZW is more commonly encountered today in a variant known as LZC, after its use in the UNIX "compress" program.
	www.faqs.org /faqs/compression-faq/part2/section-1.html (1700 words)

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