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Lempel–Ziv–Welch
Lempel–Ziv–Welch (LZW) is a universal lossless data compression algorithm created by Abraham Lempel, Jacob Ziv, and Terry Welch. It was published by Welch in 1984 as an improved implementation of the LZ78 algorithm published by Lempel and Ziv in 1978. The algorithm is simple to implement and has the potential for very high throughput in hardware implementations. It is the algorithm of the widely used Unix file compression utility compress and is used in the GIF image format. Algorithm The scenario described by Welch's 1984 paper encodes sequences of 8-bit data as fixed-length 12-bit codes. The codes from 0 to 255 represent 1-character sequences consisting of the corresponding 8-bit character, and the codes 256 through 4095 are created in a dictionary for sequences encountered in the data as it is encoded. At each stage in compression, input bytes are gathered into a sequence until the next character would make a sequence with no code yet in the dictionary. The co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Graphics Interchange Format
The Graphics Interchange Format (GIF; or , see pronunciation) is a bitmap image format that was developed by a team at the online services provider CompuServe led by American computer scientist Steve Wilhite and released on 15 June 1987. It is in widespread usage on the World Wide Web due to its wide support and portability between applications and operating systems. The format supports up to 8 bits per pixel for each image, allowing a single image to reference its own palette of up to 256 different colors chosen from the 24-bit RGB color space. It also supports animations and allows a separate palette of up to 256 colors for each frame. These palette limitations make GIF less suitable for reproducing color photographs and other images with color gradients, but well-suited for simpler images such as graphics or logos with solid areas of color. GIF images are compressed using the Lempel–Ziv–Welch (LZW) lossless data compression technique to reduce the file size wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LZ77 And LZ78
LZ77 and LZ78 are the two lossless data compression algorithms published in papers by Abraham Lempel and Jacob Ziv in 1977 and 1978. They are also known as LZ1 and LZ2 respectively. These two algorithms form the basis for many variations including LZW, LZSS, LZMA and others. Besides their academic influence, these algorithms formed the basis of several ubiquitous compression schemes, including GIF and the DEFLATE algorithm used in PNG and ZIP. They are both theoretically dictionary coders. LZ77 maintains a sliding window during compression. This was later shown to be equivalent to the ''explicit dictionary'' constructed by LZ78—however, they are only equivalent when the entire data is intended to be decompressed. Since LZ77 encodes and decodes from a sliding window over previously seen characters, decompression must always start at the beginning of the input. Conceptually, LZ78 decompression could allow random access to the input if the entire dictionary were known in ad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TIFF
Tag Image File Format, abbreviated TIFF or TIF, is an image file format for storing raster graphics images, popular among graphic artists, the publishing industry, and photographers. TIFF is widely supported by scanning, faxing, word processing, optical character recognition, image manipulation, desktop publishing, and page-layout applications. The format was created by the Aldus Corporation for use in desktop publishing. It published the latest version 6.0 in 1992, subsequently updated with an Adobe Systems copyright after the latter acquired Aldus in 1994. Several Aldus or Adobe technical notes have been published with minor extensions to the format, and several specifications have been based on TIFF 6.0, including TIFF/EP (ISO 12234-2), TIFF/IT (ISO 12639), TIFF-F (RFC 2306) and TIFF-FX (RFC 3949). History TIFF was created as an attempt to get desktop scanner vendors of the mid-1980s to agree on a common scanned image file format, in place of a multitude of proprietary for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terry Welch
Terry Archer Welch was an American computer scientist. Along with Abraham Lempel and Jacob Ziv, he developed the lossless Lempel–Ziv–Welch (LZW) compression algorithm, which was published in 1984. Education Welch received a Bachelor of Science, B.S., Master of Science, M.S. and Doctor of Philosophy, Ph.D. degree at Massachusetts Institute of Technology, MIT in electrical engineering. He taught at the University of Texas at Austin and worked in computer design at Honeywell in Waltham, Massachusetts. Career He taught at the University of Texas in Austin until joining the Sperry Corporation, Sperry Research Center, Sudbury, Massachusetts, in 1976 where the paper about the LZW algorithm was published. In 1983 he joined Digital Equipment Corporation, DEC where he worked as DEC liaison to Microelectronics and Computer Technology Corporation, MCC's advanced computer architecture program. He died of a brain tumor in 1988. References [Baidu] |
Lossless Data Compression
Lossless compression is a class of data compression that allows the original data to be perfectly reconstructed from the compressed data with no loss of information. Lossless compression is possible because most real-world data exhibits statistical redundancy. By contrast, lossy compression permits reconstruction only of an approximation of the original data, though usually with greatly improved compression rates (and therefore reduced media sizes). By operation of the pigeonhole principle, no lossless compression algorithm can efficiently compress all possible data. For this reason, many different algorithms exist that are designed either with a specific type of input data in mind or with specific assumptions about what kinds of redundancy the uncompressed data are likely to contain. Therefore, compression ratios tend to be stronger on human- and machine-readable documents and code in comparison to entropic binary data (random bytes). Lossless data compression is used in many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Abraham Lempel
Abraham Lempel ( he, אברהם למפל, born 10 February 1936) is an Israeli computer scientist and one of the fathers of the LZ family of lossless data compression algorithms. Biography Lempel was born on 10 February 1936 in Lwów, Poland (now Lviv, Ukraine). He studied at Technion - Israel Institute of Technology, and received a B.Sc. in 1963, M.Sc. in 1965, and D.Sc. in 1967. Since 1977 he has held the title of full professor. Lempel is now a professor emeritus in Technion. His historically important works start with the presentation of the LZ77 algorithm in a paper entitled "A Universal Algorithm for Sequential Data Compression" in the ''IEEE Transactions on Information Theory'' (May 1977), co-authored by Jacob Ziv. He is the recipient of the 1998 Golden Jubilee Award for Technological Innovation from the IEEE Information Theory Society; and the 2007 IEEE Richard W. Hamming Medal, for "pioneering work in data compression, especially the Lempel-Ziv algorithm". Lempel fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adobe Acrobat Reader
Adobe Acrobat is a family of application software and Web services developed by Adobe Inc. to view, create, manipulate, print and manage Portable Document Format (PDF) files. The family comprises Acrobat Reader (formerly Reader), Acrobat (formerly Exchange) and Acrobat.com. The basic Acrobat Reader, available for several desktop and mobile platforms, is freeware; it supports viewing, printing and annotating of PDF files. Additional, "Premium", services are available on paid subscription. The commercial proprietary Acrobat, available for Microsoft Windows and macOS only, can also create, edit, convert, digitally sign, encrypt, export and publish PDF files. Acrobat.com complements the family with a variety of enterprise content management and file hosting services. Purpose The main function of Adobe Acrobat is creating, viewing, and editing PDF documents. It can import popular document and image formats and save them as PDF. It is also possible to import a scanner's output, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Patent
A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A patent is not the grant of a right to make or use or sell. It does not, directly or indirectly, imply any such right. It grants only the right to exclude others. The supposition that a right to make is created by the patent grant is obviously inconsistent with the established distinctions between generic and specific patents, and with the well-known fact that a very considerable portion of the patents granted are in a field covered by a former relatively generic or basic patent, are tributary to such earlier patent, and cannot be practiced unless by license thereunder." – ''Herman v. Youngstown Car Mfg. Co.'', 191 F. 579, 584–85, 112 CCA 185 (6th Cir. 1911) In most countries, patent rights fall under private law and the patent holder mus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unisys
Unisys Corporation is an American multinational information technology (IT) services and consulting company headquartered in Blue Bell, Pennsylvania. It provides digital workplace solutions, cloud, applications, and infrastructure solutions, enterprise computing solutions, and business process solutions for organizations around the world. History Founding Unisys was formed in 1986 through the merger of mainframe corporations Sperry and Burroughs, with Burroughs buying Sperry for $4.8 billion. The name was chosen from over 31,000 submissions in an internal competition when Christian Machen submitted the word "Unisys" which was composed of parts of the words ''united'', ''information'' and ''systems''. The merger was the largest in the computer industry at the time and made Unisys the second largest computer company with annual revenue of $10.5 billion. Michael Blumenthal became CEO and Chairman. Soon after the merger, the market for proprietary mainframe-class systems—t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territories, nine Minor Outlying Islands, and 326 Indian reservations. The United States is also in free association with three Pacific Island sovereign states: the Federated States of Micronesia, the Marshall Islands, and the Republic of Palau. It is the world's third-largest country by both land and total area. It shares land borders with Canada to its north and with Mexico to its south and has maritime borders with the Bahamas, Cuba, Russia, and other nations. With a population of over 333 million, it is the most populous country in the Americas and the third most populous in the world. The national capital of the United States is Washington, D.C. and its most populous city and principal financial center is New York City. Paleo-Americ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sperry Corporation
Sperry Corporation was a major American equipment and electronics company whose existence spanned more than seven decades of the 20th century. Sperry ceased to exist in 1986 following a prolonged hostile takeover bid engineered by Burroughs Corporation, which merged the combined operation under the new name Unisys. Some of Sperry's former divisions became part of Honeywell, Lockheed Martin, Raytheon Technologies, and Northrop Grumman. The company is best known as the developer of the artificial horizon and a wide variety of other gyroscope-based aviation instruments like autopilots, bombsights, analog ballistics computers and gyro gunsights. In the post-WWII era the company branched out into electronics, both aviation related, and later, computers. History Early history The company was founded in 1910 by Elmer Ambrose Sperry, as the Sperry Gyroscope Company, to manufacture navigation equipment—chiefly his own inventions the marine gyrostabilizer and the gyrocompass—at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
