Digital Image

Information about Digital Image

A digital image is a representation of a two-dimensional image as a finite set of digital values, called picture elements or pixels. 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 colour at any specific point.

Typically, the pixels are stored in computer memory as a raster image or raster map, a two-dimensional array of small integers. These values are often transmitted or stored in a compressed form.

Digital images can be created by a variety of input devices and techniques, such as digital cameras, scanners, coordinate-measuring machines, seismographic profiling, airborne radar, and more. They can also be synthetized 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.

Image types

Each pixel of an image is typically associated to a specific 'position' in some 2D region, and has a value consisting of one or more quantities (samples) related to that position. Digital images can be classified according to the number and nature of those samples:

The term digital image is also applied to data associated to points scattered over a three-dimensional region, such as produced by tomographic equipment. In that case, each datum is called a voxel.

Image viewing

The user can utilize different program to see the image. The GIF, JPEG and PNG images can be seen simply using a web browser because they are the standard internet image formats. The SVG format is more and more used in the web and is a standard W3C format.

Some viewers offer a slideshow utility, to see the images in a certain folder one after the other automatically.

Image calibration

Proper use of a digital image usually requires knowledge of the relationship between it and the underlying phenomenon, which implies geometric and photometric (or sensor) calibration. One must also keep in mind the unavoidable errors that arise from the finite spatial resolution of the pixel array and the need to quantize each sample to a finite set of possible values.

A digital system is one that uses discrete values (often electrical voltages), representing numbers or non-numeric symbols such as letters or icons, for input, processing, transmission, storage, or display, rather than a continuous range of values (ie, as in an analog system).
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pixel (short for picture element, using the common abbreviation "pix" for "pictures") is a single point in a graphic image. Each such information element is not really a dot, nor a square, but an abstract sample.
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raster graphics image, digital image, or bitmap, is a data structure representing a generally rectangular grid of pixels, or points of color, viewable via a computer monitor, paper, or other display medium.
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Image compression is the application of Data compression on digital images. In effect, the objective is to reduce redundancy of the image data in order to be able to store or transmit data in an efficient form.

Image compression can be lossy or lossless.
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Digital imaging or digital image acquisition is the creation of digital images, typically from a physical object. The term is often assumed to imply or include the processing, compression, storage, printing, and display of such images.
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digital camera is an electronic device used to capture and store photographs digitally, instead of using photographic film like conventional cameras, or recording images in an analog format to magnetic tape like many video cameras.
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In computing, a scanner is a device that analyzes images, printed text, or handwriting, or an object (such as an ornament) and converts it to a digital image. Most scanners today are variations of the desktop (or flatbed) scanner.
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Computer graphics is a sub-field of computer science and is concerned with digitally synthesizing and manipulating visual content. Although the term often refers to three-dimensional computer graphics, it also encompasses two-dimensional graphics and image processing.
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Digital image processing is the use of computer algorithms to perform image processing on digital images. Digital image processing has the same advantages over analog image processing as digital signal processing has over analog signal processing — it allows a much wider
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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 (a continuous-time signal) to a sequence of samples (a discrete-time signal).
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binary image is a digital image that has only two possible values for each pixel.

Binary images are also called bi-level or two-level. (The names black-and-white, B&W
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In computing, a grayscale or greyscale digital image is an image in which the value of each pixel is a single sample. Displayed images of this sort are typically composed of shades of gray, varying from black at the weakest intensity to white at the strongest, though in
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A (digital) color image is a digital image that includes color information for each pixel.

For visually acceptable results, it is necessary (and almost sufficient) to provide three samples (color channels
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false-color image is an image that depicts a subject in colors that differ from those a faithful full-color photograph would show.

A true-color image of a subject is an image that appears to the human eye just like the original subject would: a green tree appears
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Multi-spectral imaging is a technology originally developed for space-based imaging. Multi-spectral imaging can capture light from frequencies beyond the visible light range, such as infrared.
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Thematic images are usually image products of classification processing of multispectral images of the earth surface. The classification process differentiates types of surface such as land, water, forest, lake, structure etc.
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A picture function is a mathematical representation of a two-dimensional image as a function of two spatial variables. The function f(x,y) describes the intensity of the point at coordinates (x,y).
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The volume of a solid object is the three-dimensional concept of how much space it occupies, often quantified numerically. One-dimensional figures (such as lines) and two-dimensional shapes (such as squares) are assigned zero volume in the three-dimensional space.
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Tomography is imaging by sections or sectioning. A device used in tomography is called a tomograph, while the image produced is a tomogram. The method is used in medicine, archaeology, biology, geophysics, oceanography, materials science and other sciences.
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A voxel (a portmanteau of the words volumetric and pixel) is a volume element, representing a value on a regular grid in three dimensional space. This is analogous to a pixel, which represents 2D image data.
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Graphics Interchange Format

A rotating globe in GIF format. The gradient blue areas of this image transition choppily, a common artifact produced when dithering is not employed.
File extension: .
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JPEG

A photo of a flower compressed with successively more lossy compression ratios from left to right.
File extension:

.jpeg, .jpg, .jpe
.jfif, .jfi, .

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PNG may stand for:

Papua New Guinea, a country in Oceania, occupying the eastern half of the island of New Guinea and numerous off-shore islands.
Portable Network Graphics, a bitmapped image format that employs lossless data compression.

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A web browser is a software application that enables a user to display and interact with text, images, videos, music and other information typically located on a Web page at a website on the World Wide Web or a local area network.
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Scalable Vector Graphics

File extension: .svg, .svgz
MIME type: image/svg+xml^[1]
Developed by: World Wide Web Consortium
Type of format: vector image format
Extended from: XML

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World Wide Web Consortium

Consortium
Founded October 1994
Founder Tim Berners-Lee
Headquarters MIT/CSAIL in USA
ERCIM in France
Keio University in Japan
and many other offices around the world

Website www.w3.
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Slideshow is a modern concatenation of "Slide Show". A slideshow is a display of a series of chosen images, which is done for artistic or instructional purposes.
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quantization error.

Many physical quantities are actually quantized by physical entities. Examples of fields where this limitation applies include electronics (due to electrons), optics (due to photons), biology (due to DNA), and chemistry (due to molecules).
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Angular resolution describes the resolving power of any image forming device such as an optical or radio telescope, a microscope, a camera, or an eye.

Definition of terms

Resolving power
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