# Digital image

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Pictures encoded as binary data

For broader coverage of this topic, see [Digital imaging](/source/Digital_imaging).

A **digital image** is an [image](/source/Image) composed of [picture elements](/source/Pixel), also known as [pixels](/source/Pixel), each with *[finite](/source/Natural_number)*, *[discrete quantities](/source/Discrete_mathematics)* of numeric representation for its [intensity](/source/Amplitude) or [gray level](/source/Gray_level) that is an output from its [two-dimensional functions](/source/Function_(mathematics)) fed as input by its [spatial coordinates](/source/Spatial_coordinates) denoted with *x*, *y* on the x-axis and y-axis, respectively.[1] An image can be [vector](/source/Vector_graphics) or [raster](/source/Raster_graphics) type. By itself, the term "digital image" usually refers to [raster images](/source/Raster_graphics) or [bitmapped](/source/Bitmap) images (as opposed to vector images).[2]

## Raster

Main article: [Raster image](/source/Raster_image)

Raster images have a finite set of [digital](/source/Digital_data) values, called *picture elements* or [pixels](/source/Pixel).[3] The digital image contains a fixed number of rows and columns of pixels.[4] 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 image](/source/Raster_graphics) or raster map, a two-dimensional array of small integers. These values are often transmitted or stored in a [compressed](/source/Image_compression) form.

Raster images can be [created](/source/Digital_imaging) by a variety of input devices and techniques, such as [digital cameras](/source/Digital_camera), [scanners](/source/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](/source/Computer_graphics). The field of [digital image processing](/source/Digital_image_processing) is the study of algorithms for their transformation.

### Raster file formats

Main article: [Raster file format](/source/Raster_file_format)

Most users come into contact with raster images through digital cameras, which use any of several [image file formats](/source/Image_file_format).

Some [digital cameras](/source/Digital_camera) give access to almost all the data captured by the camera, using a [raw image format](/source/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](/source/Trade_secrets)) for some camera makers, but there have been initiatives such as [OpenRAW](/source/OpenRAW) to influence manufacturers to release these records publicly. An alternative may be [Digital Negative (DNG)](/source/Digital_Negative), a proprietary Adobe product described as "the public, archival format for digital camera raw data".[5] 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.[6][7][8][9][10][11][12][13]

## Vector

[Vector images](/source/Vector_image) resulted from mathematical geometry ([vector](/source/Euclidean_vector)). In mathematical terms, a [vector](/source/Vector_(mathematics_and_physics)) 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 [EPS](/source/Encapsulated_PostScript), [PDF](/source/PDF), and [AI](/source/Adobe_Illustrator_Artwork).

## Image viewing

Image viewer software displayed on images. [Web browsers](/source/Web_browser) can display standard internet images formats including [JPEG](/source/JPEG), [GIF](/source/Graphics_Interchange_Format) and [PNG](/source/Portable_Network_Graphics). Some can show [SVG](/source/Scalable_Vector_Graphics) format which is a standard [W3C](/source/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 a 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](/source/Milky_Way), about 194 GB in size).[14] Such images are difficult to download and are usually browsed online through more complex [web interfaces](/source/Web_interface).

Some viewers offer a [slideshow](/source/Slideshow) utility to display a sequence of images.

## History

See also: [Digital imaging § History](/source/Digital_imaging#History), and [Digital image processing § History](/source/Digital_image_processing#History)

The first scan done by the [SEAC](/source/SEAC_(computer)) in 1957

The SEAC scanner

Early [digital fax](/source/Fax_machine#Digital) machines such as the [Bartlane cable picture transmission system](/source/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](/source/SEAC_(computer))) at [NIST](/source/NIST).[15] The advancement of digital imagery continued in the early 1960s, alongside development of the [space program](/source/Space_program) and in [medical](/source/Medicine) research. Projects at the [Jet Propulsion Laboratory](/source/Jet_Propulsion_Laboratory), [MIT](/source/MIT), [Bell Labs](/source/Bell_Labs) and the [University of Maryland](/source/University_of_Maryland%2C_College_Park), among others, used digital images to advance [satellite imagery](/source/Satellite_imagery), wirephoto standards conversion, [medical imaging](/source/Medical_physics), [videophone](/source/Videophone) technology, [character recognition](/source/Character_recognition), and photo enhancement.[16]

Rapid advances in [digital imaging](/source/Digital_imaging) began with the introduction of [MOS integrated circuits](/source/MOS_integrated_circuit) in the 1960s and [microprocessors](/source/Microprocessor) in the early 1970s, alongside progress in related [computer memory](/source/Computer_memory) storage, [display technologies](/source/Display_technologies), and [data compression](/source/Data_compression) algorithms.

The invention of computerized axial tomography ([CAT scanning](/source/CT_scan)), using [x-rays](/source/X-ray) 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](/source/Digitization) of analog images allowed the enhancement and restoration of [archaeological](/source/Archaeology) artifacts and began to be used in fields as diverse as [nuclear medicine](/source/Nuclear_medicine), [astronomy](/source/Astronomy), [law enforcement](/source/Law_enforcement_agency), [defence](/source/Defence_(military)) and [industry](/source/Private_industry).[17]

Advances in microprocessor technology paved the way for the development and marketing of [charge-coupled devices](/source/Charge-coupled_device) (CCDs) for use in a wide range of [image capture](/source/Image_capture) devices and gradually displaced the use of analog [film](/source/Photographic_film) and [tape](/source/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](/source/Computer_graphics#History) digital images to achieve a level of refinement close to [photorealism](/source/Photorealistic_rendering).[18]

### Digital image sensors

Main article: [Image sensor](/source/Image_sensor)

The first semiconductor image sensor was the CCD, developed by [Willard S. Boyle](/source/Willard_S._Boyle) and [George E. Smith](/source/George_E._Smith) at Bell Labs in 1969.[19] 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](/source/MOS_capacitor). As it was fairly straightforward to [fabricate](/source/Semiconductor_device_fabrication) 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.[20] The CCD is a semiconductor circuit that was later used in the first [digital video cameras](/source/Digital_video_camera) for [television broadcasting](/source/Television_broadcasting).[21]

Early CCD sensors suffered from [shutter lag](/source/Shutter_lag). This was largely resolved with the invention of the [pinned photodiode](/source/Pinned_photodiode) (PPD).[22] It was invented by [Nobukazu Teranishi](/source/Nobukazu_Teranishi), Hiromitsu Shiraki and Yasuo Ishihara at [NEC](/source/NEC) in 1980.[22][23] It was a [photodetector](/source/Photodetector) structure with low lag, low [noise](/source/Noise_(electronics)), high [quantum efficiency](/source/Quantum_efficiency) and low [dark current](/source/Dark_current_(physics)).[22] In 1987, the PPD began to be incorporated into most CCD devices, becoming a fixture in [consumer electronic](/source/Consumer_electronic) [video cameras](/source/Video_cameras) and then [digital still cameras](/source/Digital_still_camera). Since then, the PPD has been used in nearly all CCD sensors and then CMOS sensors.[22]

The [NMOS](/source/NMOS_logic) [active-pixel sensor](/source/Active-pixel_sensor) (APS) was invented by [Olympus](/source/Olympus_Corporation) in Japan during the mid-1980s. This was enabled by advances in MOS [semiconductor device fabrication](/source/Semiconductor_device_fabrication), with [MOSFET scaling](/source/MOSFET_scaling) reaching smaller [micron and then sub-micron](/source/List_of_semiconductor_scale_examples) levels.[24][25] The NMOS APS was fabricated by Tsutomu Nakamura's team at Olympus in 1985.[26] The [CMOS](/source/CMOS) active-pixel sensor (CMOS sensor) was later developed by [Eric Fossum](/source/Eric_Fossum)'s team at the [NASA](/source/NASA) [Jet Propulsion Laboratory](/source/Jet_Propulsion_Laboratory) in 1993.[22] By 2007, sales of CMOS sensors had surpassed CCD sensors.[27]

### Digital image compression

Main article: [Image compression](/source/Image_compression)

An important development in digital [image compression](/source/Image_compression) technology was the [discrete cosine transform](/source/Discrete_cosine_transform) (DCT), a [lossy compression](/source/Lossy_compression) technique first proposed by [Nasir Ahmed](/source/N._Ahmed) in 1972.[28] DCT compression is used in [JPEG](/source/JPEG), which was introduced by the [Joint Photographic Experts Group](/source/Joint_Photographic_Experts_Group) in 1992.[29] JPEG compresses images down to much smaller file sizes, and has become the most widely used image file format on the [Internet](/source/Internet).[30]

## Mosaic

For the artistic concept, see [Photographic mosaic](/source/Photographic_mosaic).

See also: [Image stitching](/source/Image_stitching)

In digital imaging, a *mosaic* is a combination of non-overlapping images, arranged in some [tessellation](/source/Tessellation). [Gigapixel images](/source/Gigapixel_image) are an example of such digital image mosaics. [Satellite imagery](/source/Satellite_imagery) are often mosaicked to cover Earth regions.

Interactive viewing is provided by [virtual-reality photography](/source/Virtual-reality_photography).

## See also

- [Computer printer](/source/Computer_printer)

- [DICOM](/source/DICOM)

- [Digital art](/source/Digital_art)

- [Digital geometry](/source/Digital_geometry)

- [Digital image correlation](/source/Digital_image_correlation)

- [Digital image editing](/source/Digital_image_editing)

- [Digital image processing](/source/Digital_image_processing)

- [Digital photography](/source/Digital_photography)

- [Geocoded photo](/source/Geocoded_photo)

- [Optical character recognition](/source/Optical_character_recognition)

- [Scanography](/source/Scanography)

- [Signal processing](/source/Signal_processing)

## References

1. **[^](#cite_ref-Gonzalez_2018_p._1-0)** Gonzalez, Rafael (2018). *Digital image processing*. New York, NY: Pearson. [ISBN](/source/ISBN_(identifier)) [978-0-13-335672-4](https://en.wikipedia.org/wiki/Special:BookSources/978-0-13-335672-4). [OCLC](/source/OCLC_(identifier)) [966609831](https://search.worldcat.org/oclc/966609831).

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1. **[^](#cite_ref-3)** ["DIGITAL IMAGE COMPRESSION TECHNIQUES"](https://ijret.org/volumes/2014v03/i10/IJRET20140310044.pdf) (PDF).

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1. **[^](#cite_ref-5)** [*Digital Negative (DNG) Specification*](https://www.adobe.com/products/dng/index.html) [Archived](https://web.archive.org/web/20110420165322/https://www.adobe.com/products/dng/index.html) 2011-04-20 at the [Wayback Machine](/source/Wayback_Machine). San Jose: Adobe, 2005. Vers. 1.1.0.0. p. 9. Accessed on 10 October 2007.

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1. **[^](#cite_ref-UofC_8-0)** University of Connecticut: ["Raw as Archival Still Image Format: A Consideration" by Michael J. Bennett and F. Barry Wheeler](https://digitalcommons.uconn.edu/libr_pubs/23/) [Archived](https://web.archive.org/web/20110914165511/https://digitalcommons.uconn.edu/libr_pubs/23/) 2011-09-14 at the [Wayback Machine](/source/Wayback_Machine)

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1. **[^](#cite_ref-JPGM_11-0)** The J. Paul Getty Museum - Department of Photographs: [Rapid Capture Backlog Project - Presentation](https://www.yale.edu/digitalcoffee/downloads/speedtheplowmcn2009handout.pdf) [Archived](https://web.archive.org/web/20120610105143/https://www.yale.edu/digitalcoffee/downloads/speedtheplowmcn2009handout.pdf) 2012-06-10 at the [Wayback Machine](/source/Wayback_Machine)

1. **[^](#cite_ref-786_newsa_12-0)** most important image on the internet - Electronic Media Group: [Digital Image File Formats](https://cool.conservation-us.org/coolaic/sg/emg/library/pdf/vitale/2007-07-vitale-digital_image_file_formats.pdf) [Archived](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) 2010-12-14 at the [Wayback Machine](/source/Wayback_Machine)

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1. **[^](#cite_ref-t81_29-0)** ["T.81 – Digital Compression and Coding of Continuous-Tone Still Images – Requirements and Guidelines"](https://www.w3.org/Graphics/JPEG/itu-t81.pdf) (PDF). [CCITT](/source/CCITT). September 1992. [Archived](https://web.archive.org/web/20191230093239/https://www.w3.org/Graphics/JPEG/itu-t81.pdf) (PDF) from the original on 30 December 2019. Retrieved 12 July 2019.

1. **[^](#cite_ref-30)** ["The JPEG image format explained"](https://web.archive.org/web/20190805194553/https://home.bt.com/tech-gadgets/photography/what-is-a-jpeg-11364206889349). *[BT.com](/source/BT.com)*. [BT Group](/source/BT_Group). 31 May 2018. Archived from [the original](https://home.bt.com/tech-gadgets/photography/what-is-a-jpeg-11364206889349) on 5 August 2019. Retrieved 5 August 2019.

v t e Photography Equipment Camera Box camera light-field digital field instant phone pinhole press rangefinder SLR still TLR toy view Darkroom enlarger safelight Film base format holder stock available films discontinued films Filter Flash beauty dish cucoloris gobo hot shoe lens hood monolight reflector snoot softbox Lens long-focus prime zoom wide-angle fisheye swivel telephoto Manufacturers Monopod Movie projector Slide projector Tripod head Zone plate Terminology 35 mm equivalent focal length Abbreviations list Angle of view Aperture Backscatter Black and white Chromatic aberration Circle of confusion Clipping Color balance Color temperature Depth of field Depth of focus Exposure Exposure compensation Exposure value F-number Film format 35mm large medium Film speed Focal length Guide number Hyperfocal distance Lens flare Metering mode Perspective distortion Telephoto compression Photograph Photographic printing Albumen Photographic processes Reciprocity Red-eye effect Science of photography Shutter speed Sync Zebra patterning Zone System Genres Abstract Aerial Aircraft Architectural Astrophotography Banquet Candid Conceptual Conservation Cloudscape Documentary Eclipse Ethnographic Erotic Fashion Fine-art Fire Fireworks Forensic Glamour High-speed Landscape Monochrome Nature Neues Sehen Nude Photojournalism Pictorialism Pornography Portrait Post-mortem Ruins Selfie space selfie Social documentary Sports Still life Stock Straight photography Street Underwater Vernacular Wedding Wildlife Techniques Afocal Blur Bokeh Bracketing Brenizer Burst mode Combination printing Contre-jour Crittercam (Pigeon photography) ETTR Fill flash Focus stacking Hand-colouring Harris shutter High-speed Holography Infrared Intentional camera movement Kirlian Kite aerial Lo-fi photography Lomography Long-exposure Luminogram Macro Manipulation Mordançage Multiple exposure Multi-exposure HDR capture Night Panning Panoramic Photogram Photomontage Print toning Redscale Rephotography Rollout Scanography Schlieren photography Sabattier effect Slow motion Stereoscopy Stopping down Strip Slit-scan Sprocket hole Sun printing Tilt–shift Miniature faking Time-lapse Ultraviolet Vignetting Xerography Zoom burst Composition Diagonal method Framing Headroom Lead room Rule of thirds Simplicity Golden triangle (composition) History Timeline of photography technology Albumen print Ambrotype Analog (film) photography Autochrome Lumière Calotype Camera obscura Daguerreotype Dufaycolor Heliography Lippmann plate Painted photography backdrops Photography and the law Photographic plate Salt print Tintype Visual arts Regional Albania Australia Bangladesh Canada China Colombia Denmark Greece India Japan Korea Luxembourg New Zealand Norway Philippines Serbia Slovenia Sudan Taiwan Turkey Ukraine United States Uzbekistan Vietnam Digital photography Digital camera D-SLR MILC camera back Digiscoping Comparison of digital and film photography Film scanner Image sensor CMOS APS CCD Three-CCD camera Foveon X3 sensor Photo response non-uniformity Image sharing Pixel Color photography Print film Chromogenic print Reversal film Color management color space primary color CMYK color model RGB color model Photographic processing Anthotype Bleach bypass C-41 process Carbon print Collodion process Cross processing Cyanotype Developer Digital image processing Dye coupler E-6 process Fixer Gelatin silver print Gum printing Instant film K-14 process Photogravure Print permanence Push processing Salt print Stop bath Lists Largest photographs Most expensive photographs Museums devoted to one photographer Photographs considered the most important Photographers Norwegian Polish street women Photography periodicals Related Conservation and restoration of photographs film photographic plates Polaroid art Stereoscopy Say cheese

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Adapted from the Wikipedia article [Digital image](https://en.wikipedia.org/wiki/Digital_image) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Digital_image?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.