Image

Images may be two-dimensional (e.g. a photograph) or three dimensional (e.g. a statue). They are typically produced by optical devices -- such as a cameras, mirrors, lenses, telescopes, microscopes, etc. and natural objects and phenomena, such as the human eye or water surfaces.

The word image is also used in the broader sense of any two-dimensional figure or illustration, e.g. a map, a graph, a pie chart, an abstract painting, etc. In this wider sense, images can also be produced manually (by drawing, painting, carving, etc.), by computer graphics technology, or a combination of the two (see pseudo-photograph).

A volatile image is one that exists only for a short period of time, e.g. the reflection of an object by a mirror, a projection of the sun on a wall by a pinhole camera, or a scene displayed on a cathode ray tube. A fixed image, also called hardcopy, is one that has been recorded on a material object, such as paper or textile.

A mental image exists in someone's mind: something one remembers or imagines. The subject of an image need not be real; it may be an abstract concept, such as a graph or function -- or an imaginary entity or being.

Specialized meanings

The word also has many specialized meanings in various disciplines and contexts:

• In geometric optics, a lens can produce a real image or a virtual image.
• In many other scientific and technical contexts, image usually means a two-dimensional signal -- a physical phenomenon that can be modeled as a function from a two-dimensional domain (such as the plane or a rectangle) to some set of values, usually real numbers or vectors. This sense covers not only digital images but also analog ones, such as photographs. See image processing.
• In computer graphics and digital image processing, the word image almost always means digital image or, by extension, any computer description of an image, e.g. a raster map, an image file, or a 2D computer graphics model. For embedding an image in a webpage, see HTML element#Images.
• In computer science the word image can also mean an exact (bit-by-bit) copy of the contents of some device, such as a hard disk, floppy disk, CD-ROM, etc.. In particular,
  • A core image (or core dump) is a faithful copy of the data stored in the main memory of a computer or process.
  • An executable image is a structured file containing machine instructions and data, which can be loaded into a process's virtual memory and executed. See kernel (computers).
• In mathematics, an image is a value or set of values of a function. Specifically, let f be a function from the set X to the set Y. If a is an element of X, then its image under f is the value f(a). If A is a subset of X, then its image under f is f(A) = {f(a) : a∈A}. Finally, the image of f itself is f(X), i.e. the same as the range of f.
• In finance, the image is a coefficient (stock image) that bridges a stock's fundamental value and its market price.
• In philosophy, an image is a conception or idea.
• In religion, an image is an idol or icon.
• In social psychology an image is a representation.

See also

• optics
• imaging, photography, and digital imaging
• image processing
• graphical output device

• Wikipedia:Featured pictures

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