Digital imaging
Encyclopedia
Digital imaging or digital image acquisition is the creation of digital image
s, typically from a physical scene. The term is often assumed to imply or include the processing
, compression
, storage, printing
, and display of such images. The most usual method is by digital photography
with a digital camera
but other methods are also employed.
Digital imaging was developed in the 1960s and 1970s, largely to avoid the operational weaknesses of film cameras, for scientific and military missions including the KH-11
program. As digital technology became cheaper in later decades it replaced the old film methods for many purposes.
or similar device. Alternatively, a digital image may be obtained from another image in an analog medium, such as photograph
s, photographic film
, or printed
paper, by an image scanner
or similar device. Many technical images—such as those acquired with tomographic equipment
, side-scan sonar
, or radio telescope
s—are actually obtained by complex processing of non-image data. Weather radar
maps as seen on television news are a commonplace example. The digitalization of analog real-world data is known as digitizing
, and involves sampling
(discretization) and quantization
.
Finally, a digital image can also be computed from a geometric model or mathematical formula. In this case the name image synthesis is more appropriate, and it is more often known as rendering
.
Digital image authentication is an issue for the providers and producers of digital images such as health care organizations, law enforcement agencies and insurance companies. There are methods emerging in forensic photography
to analyze a digital image and determine if it has been altered
.
Digital image
A digital image is a numeric representation of a two-dimensional image. Depending on whether or not the image resolution is fixed, it may be of vector or raster type...
s, typically from a physical scene. The term is often assumed to imply or include the processing
Digital image processing
Digital image processing is the use of computer algorithms to perform image processing on digital images. As a subcategory or field of digital signal processing, digital image processing has many advantages over analog image processing...
, compression
Image compression
The objective of image compression is to reduce irrelevance and redundancy of the image data in order to be able to store or transmit data in an efficient form.- Lossy and lossless compression :...
, storage, printing
Digital printing
Digital printing refers to methods of printing from a digital based image directly to a variety of media. It usually refers to professional printing where small run jobs from desktop publishing and other digital sources are printed using large format and/or high volume laser or inkjet printers...
, and display of such images. The most usual method is by digital photography
Digital photography
Digital photography is a form of photography that uses an array of light sensitive sensors to capture the image focused by the lens, as opposed to an exposure on light sensitive film...
with a digital camera
Digital camera
A digital camera is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor. It is the main device used in the field of digital photography...
but other methods are also employed.
Digital imaging was developed in the 1960s and 1970s, largely to avoid the operational weaknesses of film cameras, for scientific and military missions including the KH-11
KH-11
The KH-11 KENNAN, renamed CRYSTAL in 1982 and also referenced by the codenames 1010, and "Key Hole", is a type of reconnaissance satellite launched by the American National Reconnaissance Office since December 1976...
program. As digital technology became cheaper in later decades it replaced the old film methods for many purposes.
Methods
A digital photograph may be created directly from a physical scene by a cameraDigital camera
A digital camera is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor. It is the main device used in the field of digital photography...
or similar device. Alternatively, a digital image may be obtained from another image in an analog medium, such as photograph
Photograph
A photograph is an image created by light falling on a light-sensitive surface, usually photographic film or an electronic imager such as a CCD or a CMOS chip. Most photographs are created using a camera, which uses a lens to focus the scene's visible wavelengths of light into a reproduction of...
s, photographic film
Photographic film
Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts with variable crystal sizes that determine the sensitivity, contrast and resolution of the film...
, or printed
Printing
Printing is a process for reproducing text and image, typically with ink on paper using a printing press. It is often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing....
paper, by an image scanner
Image scanner
In computing, an image scanner—often abbreviated to just scanner—is a device that optically scans images, printed text, handwriting, or an object, and converts it to a digital image. Common examples found in offices are variations of the desktop scanner where the document is placed on a glass...
or similar device. Many technical images—such as those acquired with tomographic equipment
Tomography
Tomography refers to imaging by sections or sectioning, through the use of any kind of penetrating wave. A device used in tomography is called a tomograph, while the image produced is a tomogram. The method is used in radiology, archaeology, biology, geophysics, oceanography, materials science,...
, side-scan sonar
Side-scan sonar
Side-scan sonar is a category of sonar system that is used to efficiently create an image of large areas of the sea floor...
, or radio telescope
Radio telescope
A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes...
s—are actually obtained by complex processing of non-image data. Weather radar
Weather radar
Weather radar, also called weather surveillance radar and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, estimate its type . Modern weather radars are mostly pulse-Doppler radars, capable of detecting the motion of rain droplets in addition to the...
maps as seen on television news are a commonplace example. The digitalization of analog real-world data is known as digitizing
Digitizing
Digitizing or digitization is the representation of an object, image, sound, document or a signal by a discrete set of its points or samples. The result is called digital representation or, more specifically, a digital image, for the object, and digital form, for the signal...
, and involves sampling
Sampling (signal processing)
In signal processing, sampling is the reduction of a continuous signal to a discrete signal. A common example is the conversion of a sound wave to a sequence of samples ....
(discretization) and quantization
Quantization (signal processing)
Quantization, in mathematics and digital signal processing, is the process of mapping a large set of input values to a smaller set – such as rounding values to some unit of precision. A device or algorithmic function that performs quantization is called a quantizer. The error introduced by...
.
Finally, a digital image can also be computed from a geometric model or mathematical formula. In this case the name image synthesis is more appropriate, and it is more often known as rendering
Rendering (computer graphics)
Rendering is the process of generating an image from a model , by means of computer programs. A scene file contains objects in a strictly defined language or data structure; it would contain geometry, viewpoint, texture, lighting, and shading information as a description of the virtual scene...
.
Digital image authentication is an issue for the providers and producers of digital images such as health care organizations, law enforcement agencies and insurance companies. There are methods emerging in forensic photography
Forensic photography
Forensic photography, sometimes referred to as forensic imaging or crime scene photography, is the art of producing an accurate reproduction of a crime scene or an accident scene using photography for the benefit of a court or to aid in an investigation. It is part of the process of evidence...
to analyze a digital image and determine if it has been altered
Photo manipulation
Photo manipulation is the application of image editing techniques to photographs in order to create an illusion or deception , through analog or digital means.- Types of digital photo manipulation :...
.
See also
- Digital image processingDigital image processingDigital image processing is the use of computer algorithms to perform image processing on digital images. As a subcategory or field of digital signal processing, digital image processing has many advantages over analog image processing...
- Digital photographyDigital photographyDigital photography is a form of photography that uses an array of light sensitive sensors to capture the image focused by the lens, as opposed to an exposure on light sensitive film...
- Dynamic imagingDynamic imagingDynamic imaging is the amalgamation of digital imaging, image editing, and workflow automation. It is used to automate the creation of images by zooming, panning, colorize and performing other image processing and color management operations on a copy of a digital master.Dynamic imaging technology...
- Image editingImage editingImage editing encompasses the processes of altering images, whether they be digital photographs, traditional analog photographs, or illustrations. Traditional analog image editing is known as photo retouching, using tools such as an airbrush to modify photographs, or editing illustrations with any...
- Image retrievalImage retrievalAn image retrieval system is a computer system for browsing, searching and retrieving images from a large database of digital images. Most traditional and common methods of image retrieval utilize some method of adding metadata such as captioning, keywords, or descriptions to the images so that...
- Graphics file format
- Graphic image development
- Society for Imaging Science and Technology, (IS&T)
- Film recorderFilm recorderA Film Recorder is a graphical output device for transferring digital images to photographic film.All film recorders typically work in the same manner. The image is fed from a host computer as a raster stream over a digital interface...
- PhotoplotterPhotoplotterA photoplotter is an electro-mechanical-optical machine that exposes a latent image on a media, usually high-contrast monochromatic photographic film, using a light source under computer control...
External links
- Cornell University. Digital imaging tutorial
- Digital Imaging Definitions/Glossary/Terms. Digital Imaging Definitions
- Dartmouth, Hany FaridHany FaridHany Farid is the William H. Neukom 1964 Distinguished Professor of Computational Science at Dartmouth College, and chair of Dartmouth's Neukom Institute for Computational Science. Farid specializes in image analysis, human perception, and has been called the "father" of digital image forensics by...
. Digital Image Forensics