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A digital image is an image composed of pixel, also known as Pixel, each with Natural number, discrete quantities of numeric representation for its Amplitude or gray level that is an output from its two-dimensional functions fed as input by its spatial coordinates denoted with x, y on the x-axis and y-axis, respectively. An image can be vector graphics or raster graphics type. By itself, the term "digital image" usually refers to Raster graphics or Bitmap images (as opposed to vector images).
The digital image contains a fixed number of rows and columns of pixels. Pixels are the smallest individual element in an image, holding quantized values that represent the brightness of a given color at any specific point.
Typically, the pixels are stored in computer memory as a raster graphics or raster map, a two-dimensional array of small integers. These values are often transmitted or stored in a compressed form.
Raster images can be digital imaging by a variety of input devices and techniques, such as , Image scanner, coordinate-measuring machines, seismographic profiling, airborne radar, and more. They can also be synthesized from arbitrary non-image data, such as mathematical functions or three-dimensional geometric models; the latter being a major sub-area of computer graphics. The field of digital image processing is the study of algorithms for their transformation.
Some give access to almost all the data captured by the camera, using a raw image format. The Universal Photographic Imaging Guidelines (UPDIG) suggests these formats be used when possible since raw files produce the best quality images. These file formats allow the photographer and the processing agent the greatest level of control and accuracy for output. Their use is inhibited by the prevalence of proprietary information (trade secrets) for some camera makers, but there have been initiatives such as OpenRAW to influence manufacturers to release these records publicly. An alternative may be Digital Negative, a proprietary Adobe product described as "the public, archival format for digital camera raw data". Digital Negative (DNG) Specification . San Jose: Adobe, 2005. Vers. 1.1.0.0. p. 9. Accessed on 10 October 2007. Although this format is not yet universally accepted, support for the product is growing, and increasingly professional archivists and conservationists, working for respectable organizations, variously suggest or recommend DNG for archival purposes.universal photographic digital imaging guidelines (UPDIG): File formats - the raw file issue Archaeology Data Service / Digital Antiquity: Guides to Good Practice - Section 3 Archiving Raster Images - File Formats University of Connecticut: "Raw as Archival Still Image Format: A Consideration" by Michael J. Bennett and F. Barry Wheeler Inter-University Consortium for Political and Social Research: Obsolescence - File Formats and Software JISC Digital Media - Still Images: Choosing a File Format for Digital Still Images - File formats for master archive The J. Paul Getty Museum - Department of Photographs: Rapid Capture Backlog Project - Presentation most important image on the internet - Electronic Media Group: Digital Image File Formats Archives Association of British Columbia: Acquisition and Preservation Strategies (Rosaleen Hill)
Often, both raster and vector elements will be combined in one image; for example, in the case of a billboard with text (vector) and photographs (raster).
Example of vector file types are EPS, PDF, and AI.
Some scientific images can be very large (for instance, the 46 gigapixel size image of the Milky Way, about 194 GB in size). Such images are difficult to download and are usually browsed online through more complex .
Some viewers offer a slideshow utility to display a sequence of images.
Rapid advances in digital imaging began with the introduction of MOS integrated circuits in the 1960s and in the early 1970s, alongside progress in related computer memory storage, display technologies, and data compression algorithms.
The invention of computerized axial tomography (CT scan), using to produce a digital image of a "slice" through a three-dimensional object, was of great importance to medical diagnostics. As well as origination of digital images, digitization of analog images allowed the enhancement and restoration of archaeology artifacts and began to be used in fields as diverse as nuclear medicine, astronomy, law enforcement, defence and Private industry.
Advances in microprocessor technology paved the way for the development and marketing of charge-coupled devices (CCDs) for use in a wide range of image capture devices and gradually displaced the use of analog film and videotape in photography and videography towards the end of the 20th century. The computing power necessary to process digital image capture also allowed computer-generated digital images to achieve a level of refinement close to photorealism.
Early CCD sensors suffered from shutter lag. This was largely resolved with the invention of the pinned photodiode (PPD). It was invented by Nobukazu Teranishi, Hiromitsu Shiraki and Yasuo Ishihara at NEC in 1980. It was a photodetector structure with low lag, low noise, high quantum efficiency and low dark current. In 1987, the PPD began to be incorporated into most CCD devices, becoming a fixture in consumer electronic video cameras and then digital still cameras. Since then, the PPD has been used in nearly all CCD sensors and then CMOS sensors.
The NMOS logic active-pixel sensor (APS) was invented by Olympus in Japan during the mid-1980s. This was enabled by advances in MOS semiconductor device fabrication, with MOSFET scaling reaching smaller micron and then sub-micron levels. The NMOS APS was fabricated by Tsutomu Nakamura's team at Olympus in 1985. The CMOS active-pixel sensor (CMOS sensor) was later developed by Eric Fossum's team at the NASA Jet Propulsion Laboratory in 1993. By 2007, sales of CMOS sensors had surpassed CCD sensors.
Interactive viewing is provided by virtual-reality photography.
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