Commonly used in offices are variations of the desktop flatbed scanner where the document is placed on a glass window for scanning. Mechanically driven scanners that move the document are typically used for large-format documents, a rotary scanner, used for high-speed document scanning, is a type of drum scanner that uses a CCD array instead of a photomultiplier. Non-contact planetary scanners essentially photograph delicate books and documents, all these scanners produce two-dimensional images of subjects that are usually flat, but sometimes solid, 3D scanners produce information on the three-dimensional structure of solid objects. Digital cameras can be used for the same purposes as dedicated scanners, when compared to a true scanner, a camera image is subject to a degree of distortion, shadows, low contrast, and blur due to camera shake. Resolution is sufficient for less demanding applications, Digital cameras offer advantages of speed and non-contact digitizing of thick documents without damaging the book spine.
As of 2010 scanning technologies were combining 3D scanners with digital cameras to create full-color, in the biomedical research area, detection devices for DNA microarrays are called scanners as well. These scanners are high-resolution systems, similar to microscopes, the detection is done via CCD or a photomultiplier tube. Modern scanners are considered the successors of early telephotography and fax input devices and it used electromagnets to drive and synchronize movement of pendulums at the source and the distant location, to scan and reproduce images. It could transmit handwriting, signatures, or drawings within an area of up to 150 x 100mm, Édouard Belins Belinograph of 1913, scanned using a photocell and transmitted over ordinary phone lines, formed the basis for the AT&T Wirephoto service. In Europe, services similar to a wirephoto were called a Belino and it was used by news agencies from the 1920s to the mid-1990s, and consisted of a rotating drum with a single photodetector at a standard speed of 60 or 120 rpm.
They send a linear analog AM signal through standard telephone lines to receptors. Color photos were sent as three separated RGB filtered images consecutively, but only for special events due to transmission costs, Drum scanners capture image information with photomultiplier tubes, rather than the charge-coupled device arrays found in flatbed scanners and inexpensive film scanners. Modern color drum scanners use three matched PMTs, which red and green light, respectively. Light from the artwork is split into separate red, blue. Photomultipliers offer superior dynamic range and for this reason drum scanners can extract more detail from very dark areas of a transparency than flatbed scanners using CCD sensors. The smaller dynamic range of the CCD sensors, versus photomultiplier tubes, can lead to loss of shadow detail, while mechanics vary by manufacturer, most drum scanners pass light from halogen lamps though a focusing system to illuminate both reflective and transmissive originals. The drum scanner gets its name from the clear acrylic cylinder, depending on size, it is possible to mount originals up to 20x28, but maximum size varies by manufacturer.
One of the features of drum scanners is the ability to control sample area
Greenstone is a suite of software tools for building and distributing digital library collections on the Internet or CD-ROM. It is open-source, multilingual software, issued under the terms of the GNU General Public License, Greenstone is produced by the New Zealand Digital Library Project at the University of Waikato, and has been developed and distributed in cooperation with UNESCO and the Human Info NGO in Belgium. Greenstone may be used to large, searchable collections of digital documents. In addition to command line tools for digital collection building, Greenstone has a graphical Greenstone Librarians Interface used to build collections and assign metadata. Through user selected plugins, Greenstone can import digital documents in formats including text, jpg, tiff, MP3, PDF, the text, PDF, HTML and similar documents are converted into Greenstone Archive Format which is an XML equivalent format. A project on SourceForge was created in October 2005 for version 3 of Greenstone, in 2010, Greenstone version 2.83 was included, along with the Koha Integrated Library System, in an Ubuntu Live-Cd. K. T.
Anuradha and R. Sivakaminathan. Enhancing full text search capability in library automation package, A case study with Koha,2009 International Symposium on Computing and Control Proc. of CSIT vol. George Buchanan, Matt Jones and Gary Marsden, exploring small screen digital library access with the Greenstone Digital Library. Research and Advanced Technology for Digital Libraries Lecture Notes in Computer Science, 2458/2002, p. 583–596, dion Hoe-Lian Goh, Alton Chua, Davina Anqi Khoo, Emily Boon-Hui Khoo, Eric Bok-Tong Mak, and Maple Wen-Min Ng.2006. A checklist for evaluating open source library software, Online Information Review,30. Includes evaluation of Greenstone relative to digital library software. San Francisco, Morgan Kaufmann Publishers, p. 171-172, raghavan, A. Neelameghan and S. K. Lalitha. Co-creation and development of library software. Nafala, and Bimal Kanti Sen.2009, Digital archiving of audio content using WINISIS and Greenstone software, a manual for community radio managers. New Delhi, UNESCO Office New Delhi, p. 73-92, using open source systems for digital libraries.
Building Indian language digital library collections, Some experiences with Greenstone software, Digital Libraries, International Collaboration and Cross-Fertilization Lecture Notes in Computer Science,2005, 3334/2005, 189-211, doi,10. 1007/978-3-540-30544-6_92. Sharad Kumar Sonkar, Veena Makhija, Ashok Kumar, and Dr Mohinder Singh, application of Greenstone Digital Library software in newspapers clippings. DESIDOC Bulletin of Information Technology,25, 9–17, walter E. Valero, Claudia A. Perry, and Thomas T. Surprenant
Okular is the document viewer for KDE SC4. It is based on KPDF and it replaced KPDF, KGhostView, KFax, KFaxview and its functionality can be easily embedded in other applications. Okular was started for the Google Summer of Code of 2005, Okular was identified as a success story of the 2007 Season of Usability. In this season the Okular toolbar mockup was created based on an analysis of other popular document viewers, okulars annotation features include commenting on PDF documents and drawing lines, geometric shapes, adding textboxes, and stamps. Annotations are stored separately from the unmodified PDF file, or can be saved in the document as standard PDF annotations, text can be extracted to a text file. It is possible to select parts of the document and copy the text or image to the clipboard and this can be turned off in the options under Obey DRM limitations, however. List of PDF software Evince, the counterpart PDF viewer for GNOME Okular home page Okular user wiki
UTF-8 is a character encoding capable of encoding all possible characters, or code points, defined by Unicode and originally designed by Ken Thompson and Rob Pike. The encoding is variable-length and uses 8-bit code units and it was designed for backward compatibility with ASCII and to avoid the complications of endianness and byte order marks in the alternative UTF-16 and UTF-32 encodings. The name is derived from Unicode Transformation Format – 8-bit, UTF-8 is the dominant character encoding for the World Wide Web, accounting for 88. 9% of all Web pages in April 2017. The Internet Mail Consortium recommended that all programs be able to display and create mail using UTF-8. UTF-8 encodes each of the 1,112,064 valid code points in Unicode using one to four 8-bit bytes, code points with lower numerical values, which tend to occur more frequently, are encoded using fewer bytes. The following table shows the structure of the encoding, the x characters are replaced by the bits of the code point.
If the number of significant bits is no more than 7, the first line applies, if no more 11 bits, the second line applies, the first 128 characters need one byte. Three bytes are needed for characters in the rest of the Basic Multilingual Plane, four bytes are needed for characters in the other planes of Unicode, which include less common CJK characters, various historic scripts, mathematical symbols, and emoji. The salient features of this scheme are as follows, Backward compatibility, One-byte codes are used for the ASCII values 0 through 127, clear indication of byte sequence length, The first byte indicates the number of bytes in the sequence. The length of multi-byte sequences is determined as it is simply the number of high-order 1s in the leading byte. Self-synchronization, The leading bytes and the continuation bytes do not share values and this means a search will not accidentally find the sequence for one character starting in the middle of another character. It means the start of a character can be found from a position by backing up at most 3 bytes to find the leading byte.
Consider the encoding of the Euro sign, €, the Unicode code point for € is U+20AC. According to the table above, this will take three bytes to encode, since it is between U+0800 and U+FFFF. Hexadecimal 20AC is binary 0010000010101100, the two leading zeros are added because, as the scheme table shows, a three-byte encoding needs exactly sixteen bits from the code point. All continuation bytes contain exactly six bits from the code point, so the next six bits of the code point are stored in the low order six bits of the next byte, and 10 is stored in the high order two bits to mark it as a continuation byte. Finally the last six bits of the point are stored in the low order six bits of the final byte. The three bytes 111000101000001010101100 can be concisely written in hexadecimal, as E282 AC
Founded in 1885 as the original American Telephone and Telegraph Company, it was at times the worlds largest telephone company, the worlds largest cable television operator, and a regulated monopoly. At its peak in the 1950s and 1960s, it employed one million people, in 2005, AT&T was purchased by Baby Bell and former subsidiary SBC Communications for more than $16 billion. SBC changed its name to AT&T Inc, AT&T started with Bell Patent Association, a legal entity established in 1874 to protect the patent rights of Alexander Graham Bell after he invented the telephone system. Originally a verbal agreement, it was formalized in writing in 1875 as Bell Telephone Company, in 1880 the management of American Bell had created what would become AT&T Long Lines. The project was the first of its kind to create a nationwide long-distance network with a commercially viable cost-structure, the project was formally incorporated in New York State as a separate company named American Telephone and Telegraph Company on March 3,1885.
With this assets transfer, AT&T became the parent of both American Bell and the Bell System. AT&T was involved mainly in the business and, although it was a partner with RCA, was reluctant to see radio grow because such growth might diminish the demand for wired services. It established station WEAF in New York as what was termed a toll station, AT&T could provide no programming, but anyone who wished to broadcast a message could pay a toll to AT&T and air the message publicly. The original studio was the size of a telephone booth, the idea, did not take hold, because people would pay to broadcast messages only if they were sure that someone was listening. As a result, WEAF began broadcasting entertainment material, drawing amateur talent found among its employees, throughout most of the 20th century, AT&T held a monopoly on phone service in the United States and Canada through a network of companies called the Bell System. At this time, the company was nicknamed Ma Bell, on April 30,1907, Theodore Newton Vail became President of AT&T.
Vail believed in the superiority of one system and AT&T adopted the slogan One Policy, One System. This would be the philosophy for the next 70 years. Under Vail, AT&T began buying up many of the telephone companies including Western Union telegraph. Anxious to avoid action from government antitrust suits, AT&T and the government entered into an agreement known as the Kingsbury Commitment. These actions brought unwanted attention from antitrust regulators, in the Kingsbury Commitment, AT&T and the government reached an agreement that allowed AT&T to continue operating as a monopoly. While AT&T periodically faced scrutiny from regulators, this state of affairs continued until the breakup in 1984. The United States Justice Department opened the case United States v. AT&T in 1974 and this was prompted by suspicion that AT&T was using monopoly profits from its Western Electric subsidiary to subsidize the cost of its network, a violation of anti-trust law
In information technology, lossy compression or irreversible compression is the class of data encoding methods that uses inexact approximations and partial data discarding to represent the content. These techniques are used to reduce data size for storage, different versions of the photo of the cat above show how higher degrees of approximation create coarser images as more details are removed. This is opposed to data compression which does not degrade the data. The amount of data reduction possible using lossy compression is often higher than through lossless techniques. Well-designed lossy compression technology often reduces file sizes significantly before degradation is noticed by the end-user, even when noticeable by the user, further data reduction may be desirable. Lossy compression is most commonly used to compress multimedia data, especially in such as streaming media. By contrast, lossless compression is required for text and data files, such as bank records. A picture, for example, is converted to a file by considering it to be an array of dots and specifying the color.
If the picture contains an area of the color, it can be compressed without loss by saying 200 red dots instead of red dot. The original data contains an amount of information, and there is a lower limit to the size of file that can carry all the information. Basic information theory says there is an absolute limit in reducing the size of this data. When data is compressed, its entropy increases, and it cannot increase indefinitely, as an intuitive example, most people know that a compressed ZIP file is smaller than the original file, but repeatedly compressing the same file will not reduce the size to nothing. Most compression algorithms can recognize when further compression would be pointless, in many cases, files or data streams contain more information than is needed for a particular purpose. Developing lossy compression techniques as closely matched to human perception as possible is a complex task, the terms irreversible and reversible are preferred over lossy and lossless respectively for some applications, such as medical image compression, to circumvent the negative implications of loss.
The type and amount of loss can affect the utility of the images, artifacts or undesirable effects of compression may be clearly discernible yet the result still useful for the intended purpose. Or lossy compressed images may be visually lossless, or in the case of medical images and this is because uncompressed audio can only reduce file size by lowering bit rate or depth, whereas compressing audio can reduce size while maintaining bit rate and depth. This compression becomes a loss of the least significant data. From this point of view, perceptual encoding is not essentially about discarding data, and 50 pixels of blue vs. red, which are proportional to human sensitivity to each component
Horizontal and vertical density are usually the same, as most devices have square pixels, but differ on devices that have non-square pixels. PPI can describe the resolution, in pixels, of an image file, the unit is not square centimeters—a 100×100 pixel image printed in a 1 cm square has a resolution of 100 pixels per centimeter. Used this way, the measurement is meaningful when printing an image and it has become commonplace to refer to PPI as DPI, even though PPI refers to input resolution. Industry standard, good quality photographs usually require 330 pixels per inch, at 100% size and this delivers a quality factor of 2, which is optimum. The lowest acceptable quality factor is considered 1.5, which equates to printing a 225 ppi image using a 150 lpi screen onto coated paper, screen frequency is determined by the type of paper the image is printed on. An absorbent paper surface, uncoated recycled paper for instance, lets ink droplets spread —so requires a more open printing screen, input resolution can therefore be reduced to minimize file size without loss in quality, as long as the quality factor of 2 is maintained.
This is easily determined by doubling the line frequency, for example, printing on an uncoated paper stock often limits printing screen frequency to no more than 120 lpi, therefore, a quality factor of 2 is achieved with images of 240 ppi. The PPI of a display is related to the size of the display in inches. This measurement is referred to as dots per inch, though that measurement more accurately refers to the resolution of a computer printer. This figure is determined by dividing the width of the area in pixels by the width of the display area in inches. It is possible for a display to have different horizontal and vertical PPI measurements, the dot pitch of a computer display determines the absolute limit of possible pixel density. In January 2008, Kopin Corporation announced a 0.44 inch SVGA LCD with a density of 2272 PPI. In 2011 they followed this up with a 3760 DPI0. 21” diagonal VGA colour display, the manufacturer says they designed the LCD to be optically magnified, as in high-resolution eyewear devices.
Holography applications demand even greater density, as higher pixel density produces a larger image size. Spatial light modulators can reduce pixel pitch to 2.5 μm, some observations indicate that the unaided human generally cant differentiate detail beyond 300 PPI. However, this figure depends both on the distance between viewer and image, and the visual acuity. The human eye responds in a different way to a bright, high pixel density display technologies would make supersampled antialiasing obsolete, enable true WYSIWYG graphics and, potentially enable a practical “paperless office” era. For perspective, such a device at 15 inch screen size would have to more than four Full HD screens
A computer is a device that can be instructed to carry out an arbitrary set of arithmetic or logical operations automatically. The ability of computers to follow a sequence of operations, called a program, such computers are used as control systems for a very wide variety of industrial and consumer devices. The Internet is run on computers and it millions of other computers. Since ancient times, simple manual devices like the abacus aided people in doing calculations, early in the Industrial Revolution, some mechanical devices were built to automate long tedious tasks, such as guiding patterns for looms. More sophisticated electrical machines did specialized analog calculations in the early 20th century, the first digital electronic calculating machines were developed during World War II. The speed and versatility of computers has increased continuously and dramatically since then, conventionally, a modern computer consists of at least one processing element, typically a central processing unit, and some form of memory.
The processing element carries out arithmetic and logical operations, and a sequencing, peripheral devices include input devices, output devices, and input/output devices that perform both functions. Peripheral devices allow information to be retrieved from an external source and this usage of the term referred to a person who carried out calculations or computations. The word continued with the same meaning until the middle of the 20th century, from the end of the 19th century the word began to take on its more familiar meaning, a machine that carries out computations. The Online Etymology Dictionary gives the first attested use of computer in the 1640s, one who calculates, the Online Etymology Dictionary states that the use of the term to mean calculating machine is from 1897. The Online Etymology Dictionary indicates that the use of the term. 1945 under this name, theoretical from 1937, as Turing machine, devices have been used to aid computation for thousands of years, mostly using one-to-one correspondence with fingers.
The earliest counting device was probably a form of tally stick, record keeping aids throughout the Fertile Crescent included calculi which represented counts of items, probably livestock or grains, sealed in hollow unbaked clay containers. The use of counting rods is one example, the abacus was initially used for arithmetic tasks. The Roman abacus was developed from used in Babylonia as early as 2400 BC. Since then, many forms of reckoning boards or tables have been invented. In a medieval European counting house, a checkered cloth would be placed on a table, the Antikythera mechanism is believed to be the earliest mechanical analog computer, according to Derek J. de Solla Price. It was designed to calculate astronomical positions and it was discovered in 1901 in the Antikythera wreck off the Greek island of Antikythera, between Kythera and Crete, and has been dated to circa 100 BC
The Internet Archive is a San Francisco–based nonprofit digital library with the stated mission of universal access to all knowledge. As of October 2016, its collection topped 15 petabytes, in addition to its archiving function, the Archive is an activist organization, advocating for a free and open Internet. Its web archive, the Wayback Machine, contains over 150 billion web captures, the Archive oversees one of the worlds largest book digitization projects. Founded by Brewster Kahle in May 1996, the Archive is a 501 nonprofit operating in the United States. It has a budget of $10 million, derived from a variety of sources, revenue from its Web crawling services, various partnerships, donations. Its headquarters are in San Francisco, where about 30 of its 200 employees work, Most of its staff work in its book-scanning centers. The Archive has data centers in three Californian cities, San Francisco, Redwood City, and Richmond, the Archive is a member of the International Internet Preservation Consortium and was officially designated as a library by the State of California in 2007.
Brewster Kahle founded the Archive in 1996 at around the time that he began the for-profit web crawling company Alexa Internet. In October 1996, the Internet Archive had begun to archive and preserve the World Wide Web in large quantities, the archived content wasnt available to the general public until 2001, when it developed the Wayback Machine. In late 1999, the Archive expanded its collections beyond the Web archive, Now the Internet Archive includes texts, moving images, and software. It hosts a number of projects, the NASA Images Archive, the contract crawling service Archive-It. According to its web site, Most societies place importance on preserving artifacts of their culture, without such artifacts, civilization has no memory and no mechanism to learn from its successes and failures. Our culture now produces more and more artifacts in digital form, the Archives mission is to help preserve those artifacts and create an Internet library for researchers and scholars. In August 2012, the Archive announced that it has added BitTorrent to its file download options for over 1.3 million existing files, on November 6,2013, the Internet Archives headquarters in San Franciscos Richmond District caught fire, destroying equipment and damaging some nearby apartments.
The nonprofit Archive sought donations to cover the estimated $600,000 in damage, in November 2016, Kahle announced that the Internet Archive was building the Internet Archive of Canada, a copy of the archive to be based somewhere in the country of Canada. The announcement received widespread coverage due to the implication that the decision to build an archive in a foreign country was because of the upcoming presidency of Donald Trump. Kahle was quoted as saying that on November 9th in America and it was a firm reminder that institutions like ours, built for the long-term, need to design for change. For us, it means keeping our cultural materials safe, private and it means preparing for a Web that may face greater restrictions
JBIG2 is an image compression standard for bi-level images, developed by the Joint Bi-level Image Experts Group. It is suitable for both lossless and lossy compression, JBIG2 has been published in 2000 as the international standard ITU T.88, and in 2001 as ISO/IEC14492. Ideally, a JBIG2 encoder will segment the input page into regions of text, regions of halftone images, regions that are neither text nor halftones are typically compressed using a context-dependent arithmetic coding algorithm called the MQ coder. Textual regions are compressed as follows, the pixels in the regions are grouped into symbols. A dictionary of symbols is created and encoded, typically using context-dependent arithmetic coding, typically, a symbol will correspond to a character of text, but this is not required by the compression method. Halftone images may be compressed by reconstructing the image used to generate the halftone. Overall, the used by JBIG2 to compress text is very similar to the JB2 compression scheme used in the DjVu file format for coding binary images. PDF files versions 1.4 and above may contain JBIG2-compressed data, open-source decoders for JBIG2 are jbig2dec, the java-based jbig2-imageio and the decoder found in versions 2.00 and above of xpdf.
Typically, an image consists mainly of a large amount of textual and halftone data. The bi-level image is segmented into three regions, text and generic regions, each region is coded differently and the coding methodologies are described in the following passage. Text coding is based on the nature of human visual interpretation, a human observer cannot tell the difference between two instances of the same characters in a bi-level image even though they may not exactly match pixel by pixel. Therefore, only the bitmap of one representative character instance needs to be coded instead of coding the bitmaps of each occurrence of the same character individually, for each character instance, the coded instance of the character is stored into a symbol dictionary. There are two encoding methods for image data, pattern matching and substitution and soft pattern matching. These methods are presented in the following subsections, the position is usually relative to another previously coded character. If a match is not found, the segmented pixel block is coded directly, typical procedures of pattern matching and substitution algorithm are displayed in the left block diagram of the figure above.
Although the method of PM&S can achieve outstanding compression, substitution errors could be made during the process if the resolution is low. The deployment of refinement data can make the character-substitution error mentioned earlier highly unlikely, the refinement data contains the current desired character instance, which is coded using the pixels of both the current character and the matching character in the dictionary. Since it is known that the current character instance is highly correlated with the matched character, halftone images can be compressed using two methods
Rendering (computer graphics)
Rendering or image synthesis is the process of generating an image from a 2D or 3D model by means of computer programs. Also, the results of such a model can be called a rendering, a scene file contains objects in a strictly defined language or data structure, it would contain geometry, texture and shading information as a description of the virtual scene. The data contained in the file is passed to a rendering program to be processed. The term rendering may be by analogy with a rendering of a scene. A GPU is a device able to assist a CPU in performing complex rendering calculations. If a scene is to look realistic and predictable under virtual lighting. The rendering equation doesnt account for all lighting phenomena, but is a lighting model for computer-generated imagery. Rendering is used to describe the process of calculating effects in an editing program to produce final video output. Rendering is one of the major sub-topics of 3D computer graphics, in the graphics pipeline, it is the last major step, giving the final appearance to the models and animation.
With the increasing sophistication of computer graphics since the 1970s, it has become a distinct subject. Rendering has uses in architecture, video games, movie or TV visual effects, as a product, a wide variety of renderers are available. Some are integrated into larger modeling and animation packages, some are stand-alone, on the inside, a renderer is a carefully engineered program, based on a selective mixture of disciplines related to, light physics, visual perception and software development. In the case of 3D graphics, rendering may be slowly, as in pre-rendering. When the pre-image is complete, rendering is used, which adds in bitmap textures or procedural textures, bump mapping, the result is a completed image the consumer or intended viewer sees. For movie animations, several images must be rendered, and stitched together in a program capable of making an animation of this sort, most 3D image editing programs can do this. A rendered image can be understood in terms of a number of visible features, Rendering research and development has been largely motivated by finding ways to simulate these efficiently.
Some relate directly to particular algorithms and techniques, while others are produced together, Tracing every particle of light in a scene is nearly always completely impractical and would take a stupendous amount of time. Even tracing a portion large enough to produce an image takes an amount of time if the sampling is not intelligently restricted