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Run-length Encoding
Run-length encoding (RLE) is a form of lossless data compression in which ''runs'' of data (sequences in which the same data value occurs in many consecutive data elements) are stored as a single data value and count, rather than as the original run. This is most efficient on data that contains many such runs, for example, simple graphic images such as icons, line drawings, Conway's Game of Life, and animations. For files that do not have many runs, RLE could increase the file size. RLE may also be used to refer to an early graphics file format supported by CompuServe for compressing black and white images, but was widely supplanted by their later Graphics Interchange Format (GIF). RLE also refers to a little-used image format in Windows 3.x, with the extension rle, which is a run-length encoded bitmap, used to compress the Windows 3.x startup screen. Example Consider a screen containing plain black text on a solid white background. There will be many long runs of white pixel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [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] |
JPEG
JPEG ( ) is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography. The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality. Since its introduction in 1992, JPEG has been the most widely used image compression standard in the world, and the most widely used digital image format, with several billion JPEG images produced every day as of 2015. The term "JPEG" is an acronym for the Joint Photographic Experts Group, which created the standard in 1992. JPEG was largely responsible for the proliferation of digital images and digital photos across the Internet, and later social media. JPEG compression is used in a number of image file formats. JPEG/Exif is the most common image format used by digital cameras and other photographic image capture devices; along with JPEG ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Recursive Indexing
{{no footnotes, date=June 2020 Recursive indexing is an algorithm used to represent large numberic values using members of a relatively small set. Recursive indexing writes the successive differences of the number after extracting the maximum value of the alphabet set from the number, and continuing recursively till the difference falls in the range of the set. Recursive indexing with a 2-letter alphabet is called unary code Unary may refer to: *Unary numeral system, the simplest numeral system to represent natural numbers *Unary function, a function that takes one argument; in computer science, a unary operator is a subset of unary function *Unary operation, a kind of .... Encoding To encode a number ''N'', keep reducing the maximum element of this set (''S''max) from ''N'' and output ''S''max for each such difference, stopping when the number lies in the half closed half open range – ''S''max). Example Let ''S'' = [0 1 2 3 4 … 10 be an 11-element se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Burrows–Wheeler Transform
The Burrows–Wheeler transform (BWT, also called block-sorting compression) rearranges a character string into runs of similar characters. This is useful for compression, since it tends to be easy to compress a string that has runs of repeated characters by techniques such as move-to-front transform and run-length encoding. More importantly, the transformation is ''reversible'', without needing to store any additional data except the position of the first original character. The BWT is thus a "free" method of improving the efficiency of text compression algorithms, costing only some extra computation. The Burrows–Wheeler transform is an algorithm used to prepare data for use with data compression techniques such as bzip2. It was invented by Michael Burrows and David Wheeler in 1994 while Burrows was working at DEC Systems Research Center in Palo Alto, California. It is based on a previously unpublished transformation discovered by Wheeler in 1983. The algorithm can be imple ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Golomb Coding
Golomb coding is a lossless data compression method using a family of data compression codes invented by Solomon W. Golomb in the 1960s. Alphabets following a geometric distribution will have a Golomb code as an optimal prefix code, making Golomb coding highly suitable for situations in which the occurrence of small values in the input stream is significantly more likely than large values. Rice coding Rice coding (invented by Robert F. Rice) denotes using a subset of the family of Golomb codes to produce a simpler (but possibly suboptimal) prefix code. Rice used this set of codes in an adaptive coding scheme; "Rice coding" can refer either to that adaptive scheme or to using that subset of Golomb codes. Whereas a Golomb code has a tunable parameter that can be any positive integer value, Rice codes are those in which the tunable parameter is a power of two. This makes Rice codes convenient for use on a computer since multiplication and division by 2 can be implemented more e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Comparison Of Graphics File Formats
This is a comparison of image file formats (graphics file formats). This comparison primarily features file formats for 2D images. General Ownership of the format and related information. Technical details See also * List of codecs References {{Graphics file formats Graphics File Formats An Image file format is a file format for a digital image. There are many formats that can be used, such as JPEG, PNG, and GIF. Most formats up until 2022 were for storing 2D images, not 3D ones. The data stored in an image file format may be c ... * Graphics file ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Look-and-say Sequence
In mathematics, the look-and-say sequence is the integer sequence, sequence of integers beginning as follows: : 1, 11, 21, 1211, 111221, 312211, 13112221, 1113213211, 31131211131221, ... . To generate a member of the sequence from the previous member, read off the digits of the previous member, counting the number of digits in groups of the same digit. For example: * 1 is read off as "one 1" or 11. * 11 is read off as "two 1s" or 21. * 21 is read off as "one 2, one 1" or 1211. * 1211 is read off as "one 1, one 2, two 1s" or 111221. * 111221 is read off as "three 1s, two 2s, one 1" or 312211. The look-and-say sequence was analyzed by John Horton Conway, John Conway Reprinted as after he was introduced to it by one of his students at a party. The idea of the look-and-say sequence is similar to that of run-length encoding. If started with any digit ''d'' from 0 to 9 then ''d'' will remain indefinitely as the last digit of the sequence. For any ''d'' other than 1, the sequence ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kolakoski Sequence
In mathematics, the Kolakoski sequence, sometimes also known as the Oldenburger–Kolakoski sequence, is an infinite sequence of symbols that is the sequence of run lengths in its own run-length encoding. It is named after the recreational mathematician William Kolakoski (1944–97) who described it in 1965, but it was previously discussed by Rufus Oldenburger in 1939. Definition The initial terms of the Kolakoski sequence are: :1,2,2,1,1,2,1,2,2,1,2,2,1,1,2,1,1,2,2,1,2,1,1,2,1,2,2,1,1,... Each symbol occurs in a "run" (a sequence of equal elements) of either one or two consecutive terms, and writing down the lengths of these runs gives exactly the same sequence: :1,2,2,1,1,2,1,2,2,1,2,2,1,1,2,1,1,2,2,1,2,1,1,2,1,2,2,1,1,2,1,1,2,1,2,2,1,2,2,1,1,2,1,2,2,... :1, 2 , 2 ,1,1, 2 ,1, 2 , 2 ,1, 2 , 2 ,1,1, 2 ,1,1, 2 , 2 ,1, 2 ,1,1, 2 ,1, 2 , 2&n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Modified Huffman Coding
Modified Huffman coding is used in fax machines to encode black-on-white images (bitmaps). It combines the variable-length codes of Huffman coding with the coding of repetitive data in run-length encoding. The basic Huffman coding provides a way to compress files that have much repeating data, like a file containing text, where the alphabet letters are the repeating objects. However, a single scan line contains only two kinds of elements white pixels and black pixels which can be represented directly as a 0 and 1. This "alphabet" of only two symbols is too small to directly apply the Huffman coding. But if we first use run-length encoding, we can have more objects to encode. Here is an example taken from the article on run-length encoding Run-length encoding (RLE) is a form of lossless data compression in which ''runs'' of data (sequences in which the same data value occurs in many consecutive data elements) are stored as a single data value and count, rather than as the original ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Telecommunication Union
The International Telecommunication Union is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on 17 May 1865 as the International Telegraph Union, making it the oldest UN agency. The ITU was initially aimed at helping connect telegraphic networks between countries, with its mandate consistently broadening with the advent of new communications technologies; it adopted its current name in 1932 to reflect its expanded responsibilities over radio and the telephone. On 15 November 1947, the ITU entered into an agreement with the newly created United Nations to become a specialized agency within the UN system, which formally entered into force on 1 January 1949. The ITU promotes the shared global use of the radio spectrum, facilitates international cooperation in assigning satellite orbits, assists in developing and coordinating worldwide technical standards, and works to improve tele ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ILBM
Interleaved Bitmap (ILBM) is an image file format conforming to the Interchange File Format (IFF) standard. The format originated on the Amiga platform, and on IBM-compatible systems, files in this format or the related PBM (Planar Bitmap) format are typically encountered in games from late 1980s and early 1990s that were either Amiga ports or had their graphical assets designed on Amiga machines. A characteristic feature of the format is that it stores bitmaps in the form of interleaved bit planes, which gives the format its name; this reflects the way the Amiga graphics hardware natively reads graphics data from memory. A simple form of compression is supported to make ILBM files more compact. On the Amiga, these files are not associated with a particular file extension, though as they started being used on PC systems where extensions are systematically used, they employed a ''.lbm'' or occasionally a ''.bbm'' extension. File format ILBM is an implementation of the IFF fil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MacPaint
MacPaint is a raster graphics editor developed by Apple Computer and released with the original Macintosh personal computer on January 24, 1984. It was sold separately for US$195 with its word processing counterpart, MacWrite. MacPaint was notable because it could generate graphics that could be used by other applications. Using the mouse, and the clipboard and QuickDraw picture language, pictures could be cut from MacPaint and pasted into MacWrite documents.. The original MacPaint was developed by Bill Atkinson, a member of Apple's original Macintosh development team. Early development versions of MacPaint were called MacSketch, still retaining part of the name of its roots, LisaSketch. It was later developed by Claris, the software subsidiary of Apple which was formed in 1987. The last version of MacPaint was version 2.0, released in 1988. It was discontinued by Claris in 1998 because of diminishing sales. Development MacPaint was written by Bill Atkinson, a member of App ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
