Editing Digital image

{{Short description|Pictures encoded as binary data}}
{{Use American English|date=January 2019}}
{{broader|Digital imaging}}

A '''digital image''' is an [[image]] composed of [[pixel|picture element]]s, also known as [[Pixel|pixels]], each with ''[[Natural number|finite]]'', ''[[discrete mathematics|discrete quantities]]'' of numeric representation for its [[Amplitude|intensity]] or [[gray level]] that is an output from its [[Function (mathematics)|two-dimensional functions]] fed as input by its [[spatial coordinates]] denoted with ''x'', ''y'' on the x-axis and y-axis, respectively.<ref name="Gonzalez 2018 p. ">{{cite book | last=Gonzalez | first=Rafael | title=Digital image processing | publisher=Pearson | location=New York, NY | year=2018 | isbn=978-0-13-335672-4 | oclc=966609831 }}</ref> Depending on whether the [[image resolution]] is fixed, it may be of [[vector graphics|vector]] or [[raster graphics|raster]] type. {{citation needed span|By itself, the term "digital image" usually refers to [[raster graphics|raster images]] or [[bitmap]]ped images (as opposed to [[vector graphics|vector images]]).|date=December 2019}}

==Raster==
{{main|Raster image}}
Raster images have a finite set of [[Digital data|digital]] values, called ''picture elements'' or [[pixel]]s. 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|raster image]] or raster map, a two-dimensional array of small integers. These values are often transmitted or stored in a [[image compression|compressed]] form.

Raster images can be [[digital imaging|created]] by a variety of input devices and techniques, such as [[digital camera]]s, [[Image scanner|scanner]]s, 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.

===Raster file formats===
{{main|Raster file format}}
Most users come into contact with raster images through digital cameras, which use any of several [[image file formats]].

Some [[digital camera]]s 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 (file format)|Digital Negative (DNG)]], a proprietary Adobe product described as "the public, archival format for digital camera raw data".<ref>[https://www.adobe.com/products/dng/index.html ''Digital Negative (DNG) Specification''] {{Webarchive|url=https://web.archive.org/web/20110420165322/https://www.adobe.com/products/dng/index.html |date=2011-04-20 }}. San Jose: Adobe, 2005. Vers. 1.1.0.0. p. 9. Accessed on October 10, 2007.</ref> 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.<ref name="UPDIG">universal photographic digital imaging guidelines (UPDIG): [https://www.updig.org/guidelines/ph_file_formats.html File formats - the raw file issue] {{Webarchive|url=https://web.archive.org/web/20111020052554/https://www.updig.org/guidelines/ph_file_formats.html |date=2011-10-20 }}</ref><ref name="ADSDA">Archaeology Data Service / Digital Antiquity: [https://guides.archaeologydataservice.ac.uk/g2gp/RasterImg_3 Guides to Good Practice - Section 3 Archiving Raster Images - File Formats] {{Webarchive|url=https://web.archive.org/web/20111214082154/https://guides.archaeologydataservice.ac.uk/g2gp/RasterImg_3 |date=2011-12-14 }}</ref><ref name="UofC">University of Connecticut: [https://digitalcommons.uconn.edu/libr_pubs/23/ "Raw as Archival Still Image Format: A Consideration" by Michael J. Bennett and F. Barry Wheeler] {{Webarchive|url=https://web.archive.org/web/20110914165511/https://digitalcommons.uconn.edu/libr_pubs/23/ |date=2011-09-14 }}</ref><ref name="IUCPSR">Inter-University Consortium for Political and Social Research: [https://www.icpsr.umich.edu/dpm/dpm-eng/oldmedia/obsolescence1.html Obsolescence - File Formats and Software] {{Webarchive|url=https://web.archive.org/web/20111102185230/https://www.icpsr.umich.edu/dpm/dpm-eng/oldmedia/obsolescence1.html |date=2011-11-02 }}</ref><ref name="JISC">JISC Digital Media - Still Images: [https://www.jiscdigitalmedia.ac.uk/stillimages/advice/choosing-a-file-format-for-digital-still-images/#fo3 Choosing a File Format for Digital Still Images - File formats for master archive] {{Webarchive|url=https://web.archive.org/web/20111116002515/https://www.jiscdigitalmedia.ac.uk/stillimages/advice/choosing-a-file-format-for-digital-still-images#fo3 |date=2011-11-16 }}</ref><ref name="JPGM">The J. Paul Getty Museum - Department of Photographs: [https://www.yale.edu/digitalcoffee/downloads/speedtheplowmcn2009handout.pdf Rapid Capture Backlog Project - Presentation] {{Webarchive|url=https://web.archive.org/web/20120610105143/https://www.yale.edu/digitalcoffee/downloads/speedtheplowmcn2009handout.pdf |date=2012-06-10 }}</ref><ref name="786 newsa">most important image on the internet - Electronic Media Group: [https://cool.conservation-us.org/coolaic/sg/emg/library/pdf/vitale/2007-07-vitale-digital_image_file_formats.pdf Digital Image File Formats] {{Webarchive|url=https://web.archive.org/web/20101214052741/https://cool.conservation-us.org/coolaic/sg/emg/library/pdf/vitale/2007-07-vitale-digital_image_file_formats.pdf |date=2010-12-14 }}</ref><ref name="AABC">Archives Association of British Columbia: [https://786news.com/top-15-most-important-image-on-the-internet-that-people-often-to-search-for/ Acquisition and Preservation Strategies (Rosaleen Hill)]</ref>

==Vector==
[[Vector image]]s resulted from mathematical geometry ([[Euclidean vector|vector]]). In mathematical terms, a [[Vector (mathematics and physics)|vector]] consists of both a magnitude, or length, and a direction.

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 [[Encapsulated PostScript|EPS]], [[PDF]], and [[Adobe Illustrator Artwork|AI]].

==Image viewing==

Image viewer software displayed on images. [[Web browser]]s can display standard internet images formats including [[JPEG]], [[Graphics Interchange Format|GIF]] and [[Portable Network Graphics|PNG]]. Some can show [[Scalable Vector Graphics|SVG]] format which is a standard [[W3C]] format. In the past, when the Internet was still slow, it was common to provide "preview" images that would load and appear on the website before being replaced by the main image (to give at preliminary impression). Now Internet is fast enough and this preview image is seldom used.

Some scientific images can be very large (for instance, the 46 gigapixel size image of the [[Milky Way]], about 194 Gb in size).<ref>{{cite web|url=https://www.techradar.com/news/world-of-tech/this-is-the-milky-way-in-46-billion-pixels-1307463|title=This 46-Gigapixel photo of the Milky Way will blow your mind|date=23 October 2015|access-date=5 July 2018|archive-date=5 July 2018|archive-url=https://web.archive.org/web/20180705233640/https://www.techradar.com/news/world-of-tech/this-is-the-milky-way-in-46-billion-pixels-1307463|url-status=live}}</ref> Such images are difficult to download and are usually browsed online through more complex [[web interfaces]].

Some viewers offer a [[slideshow]] utility to display a sequence of images.

==History==
{{See|Digital imaging#History|Digital image processing#History}}
[[File:NBSFirstScanImageRestored.jpg|right|thumb|The first scan done by the [[SEAC (computer)|SEAC]] in 1957]]
[[File:SEACComputer 031.jpg|right|thumb|The SEAC scanner]]

Early [[Fax machine#Digital|digital fax]] machines such as the [[Bartlane cable picture transmission system]] preceded digital cameras and computers by decades.
The first picture to be scanned, stored, and recreated in digital pixels was displayed on the Standards Eastern Automatic Computer ([[SEAC (computer)|SEAC]]) at [[NIST]].<ref>[https://www.sciencecodex.com/fiftieth_anniversary_of_first_digital_image''Fiftieth Anniversary of First Digital Image''] {{Webarchive|url=https://web.archive.org/web/20101014030023/https://www.sciencecodex.com/fiftieth_anniversary_of_first_digital_image |date=2010-10-14 }}.</ref> The advancement of digital imagery continued in the early 1960s, alongside development of the [[space program]] and in [[medicine|medical]] research. Projects at the [[Jet Propulsion Laboratory]], [[MIT]], [[Bell Labs]] and the [[University of Maryland, College Park|University of Maryland]], among others, used digital images to advance [[satellite imagery]], wirephoto standards conversion, [[medical physics|medical imaging]], [[videophone]] technology, [[character recognition]], and photo enhancement.<ref>Azriel Rosenfeld, ''Picture Processing by Computer'', New York: Academic Press, 1969</ref>

Rapid advances in [[digital imaging]] began with the introduction of [[MOS integrated circuit]]s in the 1960s and [[microprocessor]]s in the early 1970s, alongside progress in related [[computer memory]] storage, [[display technologies]], and [[data compression]] algorithms.

The invention of computerized axial tomography ([[CAT scanning]]), using [[x-ray]]s 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|archaeological]] artifacts and began to be used in fields as diverse as [[nuclear medicine]], [[astronomy]], [[Law enforcement agency|law enforcement]], [[defence (military)|defence]] and [[Private industry|industry]].<ref>
{{cite book
  | last = Gonzalez
  | first = Rafael, C
  |author2=Woods, Richard E
  | title = Digital Image Processing, 3rd Edition
  | publisher = Pearson Prentice Hall
  | year = 2008
  | page = 577
  | url = https://books.google.com/books?id=8uGOnjRGEzoC&q=%22digital+image+processing%22+gonzalez
  | isbn = 978-0-13-168728-8}}
</ref>

Advances in microprocessor technology paved the way for the development and marketing of [[charge-coupled device]]s (CCDs) for use in a wide range of [[image capture]] devices and gradually displaced the use of analog [[photographic film|film]] and [[videotape|tape]] in photography and videography towards the end of the 20th century. The computing power necessary to process digital image capture also allowed [[computer graphics#History|computer-generated]] digital images to achieve a level of refinement close to [[Photorealistic rendering|photorealism]].<ref>
{{cite book
  | last = Jähne
  | first = Bernd
  | title = Spatio-temporal image processing, Theory and Scientific Applications
  | publisher = Springer Verlag
  | year = 1993
  | page = 208
  | url = https://books.google.com/books?id=gO6V5gh4IXsC&q=Spatio-temporal+image+processing
  | isbn = 3-540-57418-2}}
</ref>

===Digital image sensors===
{{Main|Image sensor}}

The first semiconductor image sensor was the CCD, developed by [[Willard S. Boyle]] and [[George E. Smith]] at Bell Labs in 1969.<ref>{{Cite book | title = Scientific charge-coupled devices | author = James R. Janesick | publisher = SPIE Press | year = 2001 | isbn = 978-0-8194-3698-6 | pages = 3–4 | url = https://books.google.com/books?id=3GyE4SWytn4C&pg=PA3 | access-date = 2020-06-06 | archive-date = 2020-11-15 | archive-url = https://web.archive.org/web/20201115062950/https://books.google.com/books?id=3GyE4SWytn4C&pg=PA3 | url-status = live }}</ref> While researching MOS technology, they realized that an electric charge was the analogy of the magnetic bubble and that it could be stored on a tiny [[MOS capacitor]]. As it was fairly straightforward to [[semiconductor device fabrication|fabricate]] a series of MOS capacitors in a row, they connected a suitable voltage to them so that the charge could be stepped along from one to the next.<ref name="Williams">{{cite book|last1=Williams|first1=J. B.|url=https://books.google.com/books?id=v4QlDwAAQBAJ&pg=PA245|title=The Electronics Revolution: Inventing the Future|date=2017|publisher=Springer|isbn=978-3-319-49088-5|pages=245–8|access-date=2019-10-10|archive-date=2020-11-15|archive-url=https://web.archive.org/web/20201115080239/https://books.google.com/books?id=v4QlDwAAQBAJ&pg=PA245|url-status=live}}</ref> The CCD is a semiconductor circuit that was later used in the first [[digital video camera]]s for [[television broadcasting]].<ref>{{cite journal|last1=Boyle|first1=William S|last2=Smith|first2=George E.|date=1970|title=Charge Coupled Semiconductor Devices|journal=Bell Syst. Tech. J.|volume=49|issue=4|pages=587–593|doi=10.1002/j.1538-7305.1970.tb01790.x|bibcode=1970BSTJ...49..587B }}</ref>

Early CCD sensors suffered from [[shutter lag]]. This was largely resolved with the invention of the [[pinned photodiode]] (PPD).<ref name="Fossum2014"/> It was invented by [[Nobukazu Teranishi]], Hiromitsu Shiraki and Yasuo Ishihara at [[NEC]] in 1980.<ref name="Fossum2014"/><ref>{{US patent|4484210|U.S. Patent 4,484,210: Solid-state imaging device having a reduced image lag}}</ref> It was a [[photodetector]] structure with low lag, low [[noise (electronics)|noise]], high [[quantum efficiency]] and low [[dark current (physics)|dark current]].<ref name="Fossum2014"/> In 1987, the PPD began to be incorporated into most CCD devices, becoming a fixture in [[consumer electronic]] [[video cameras]] and then [[digital still camera]]s. Since then, the PPD has been used in nearly all CCD sensors and then CMOS sensors.<ref name="Fossum2014"/>

The [[NMOS logic|NMOS]] [[active-pixel sensor]] (APS) was invented by [[Olympus Corporation|Olympus]] in Japan during the mid-1980s. This was enabled by advances in MOS [[semiconductor device fabrication]], with [[MOSFET scaling]] reaching smaller [[List of semiconductor scale examples|micron and then sub-micron]] levels.<ref name=fossum93>{{cite book |last1=Fossum |first1=Eric R. |chapter=Active pixel sensors: Are CCDS dinosaurs? |author1-link=Eric Fossum |title=Charge-Coupled Devices and Solid State Optical Sensors III |journal=SPIE Proceedings Vol. 1900: Charge-Coupled Devices and Solid State Optical Sensors III |date=12 July 1993 |volume=1900 |doi=10.1117/12.148585 |publisher=International Society for Optics and Photonics |pages=2–14 |bibcode=1993SPIE.1900....2F |editor1-last=Blouke |editor1-first=Morley M.|citeseerx=10.1.1.408.6558 |s2cid=10556755 }}</ref><ref>{{cite web |last1=Fossum |first1=Eric R. |author1-link=Eric Fossum |date=2007 |title=Active Pixel Sensors |website=Eric Fossum |url=https://ericfossum.com/Publications/Papers/Active%20Pixel%20Sensors%20LASER%20FOCUS.pdf |s2cid=18831792}}</ref> The NMOS APS was fabricated by Tsutomu Nakamura's team at Olympus in 1985.<ref>{{cite journal |last1=Matsumoto |first1=Kazuya |last2=Nakamura |first2=Tsutomu |last3=Yusa |first3=Atsushi |last4=Nagai |first4=Shohei |display-authors=1|date=1985 |title=A new MOS phototransistor operating in a non-destructive readout mode |journal=Japanese Journal of Applied Physics |volume=24 |issue=5A |page=L323|doi=10.1143/JJAP.24.L323 |bibcode=1985JaJAP..24L.323M |s2cid=108450116 }}</ref> The [[CMOS]] active-pixel sensor (CMOS sensor) was later developed by [[Eric Fossum]]'s team at the [[NASA]] [[Jet Propulsion Laboratory]] in 1993.<ref name="Fossum2014">{{cite journal |last1=Fossum |first1=Eric R. |author1-link=Eric Fossum |last2=Hondongwa |first2=D. B. |title=A Review of the Pinned Photodiode for CCD and CMOS Image Sensors |journal=IEEE Journal of the Electron Devices Society |date=2014 |volume=2 |issue=3 |pages=33–43 |doi=10.1109/JEDS.2014.2306412 |doi-access=free }}</ref> By 2007, sales of CMOS sensors had surpassed CCD sensors.<ref>{{cite news |title=CMOS Image Sensor Sales Stay on Record-Breaking Pace |url=https://www.icinsights.com/news/bulletins/CMOS-Image-Sensor-Sales-Stay-On-RecordBreaking-Pace/ |access-date=6 October 2019 |work=IC Insights |date=May 8, 2018 |archive-date=21 June 2019 |archive-url=https://web.archive.org/web/20190621180401/https://www.icinsights.com/news/bulletins/CMOS-Image-Sensor-Sales-Stay-On-RecordBreaking-Pace/ |url-status=live }}</ref>

===Digital image compression===
{{Main|Image compression}}

An important development in digital [[image compression]] technology was the [[discrete cosine transform]] (DCT), a [[lossy compression]] technique first proposed by [[N. Ahmed|Nasir Ahmed]] in 1972.<ref name="Ahmed">{{cite journal |last=Ahmed |first=Nasir |author-link=N. Ahmed |title=How I Came Up With the Discrete Cosine Transform |journal=[[Digital Signal Processing (journal)|Digital Signal Processing]] |date=January 1991 |volume=1 |issue=1 |pages=4–5 |doi=10.1016/1051-2004(91)90086-Z |bibcode=1991DSP.....1....4A |url=https://www.scribd.com/doc/52879771/DCT-History-How-I-Came-Up-with-the-Discrete-Cosine-Transform |access-date=2019-09-14 |archive-date=2016-06-10 |archive-url=https://web.archive.org/web/20160610013109/https://www.scribd.com/doc/52879771/DCT-History-How-I-Came-Up-with-the-Discrete-Cosine-Transform |url-status=live |url-access=subscription }}</ref> DCT compression is used in [[JPEG]], which was introduced by the [[Joint Photographic Experts Group]] in 1992.<ref name="t81">{{cite web |title=T.81 – Digital Compression and Coding of Continuous-Tone Still Images – Requirements and Guidelines |url=https://www.w3.org/Graphics/JPEG/itu-t81.pdf |publisher=[[CCITT]] |date=September 1992 |access-date=12 July 2019 |archive-date=30 December 2019 |archive-url=https://web.archive.org/web/20191230093239/https://www.w3.org/Graphics/JPEG/itu-t81.pdf |url-status=live }}</ref> JPEG compresses images down to much smaller file sizes, and has become the most widely used image file format on the [[Internet]].<ref>{{cite web |title=The JPEG image format explained |url=https://home.bt.com/tech-gadgets/photography/what-is-a-jpeg-11364206889349 |website=[[BT.com]] |publisher=[[BT Group]] |access-date=5 August 2019 |date=31 May 2018 |archive-date=5 August 2019 |archive-url=https://web.archive.org/web/20190805194553/https://home.bt.com/tech-gadgets/photography/what-is-a-jpeg-11364206889349 }}</ref>

==Mosaic==
{{for|the artistic concept|Photographic mosaic}}
{{see also|Image stitching}}

In digital imaging, a ''mosaic'' is a combination of non-overlapping images, arranged in some [[tessellation]]. 
[[Gigapixel image]]s are an example of such digital image mosaics.
[[Satellite imagery]] are often mosaicked to cover Earth regions.

Interactive viewing is provided by [[virtual-reality photography]].

==See also==
{{Div col|small=yes}}
* [[Computer printer]]
* [[DICOM]]
* [[Digital art]]
* [[Digital geometry]]
* [[Digital image correlation]]
* [[Digital image editing]]
* [[Digital image processing]]
* [[Digital photography]]
* [[Geocoded photo]]
* [[Optical character recognition]]
* [[Scanography]] 
* [[Signal processing]]
{{Div col end}}

==References==
{{Reflist|2}}

{{photography subject}}

{{DEFAULTSORT:Digital Image}}
[[Category:Image processing]]
[[Category:Digital geometry]]
[[Category:Digital imaging]]