Image

In common usage, an image (from Latin imago) or picture is an artefact that reproduces the likeness of some subject -- usually a physical object or a person.

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 also 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.

In geometric optics, the word image has a precise technical sense: see real image and 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. In these contexts, many of the signal processing concepts that apply to one-dimensional signals -- such as resolution, dynamic range, bandwidth, filtering, etc. -- apply to images as well. See also 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. See also digital imaging, digital image processing, graphical output device.

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.

A related computer science usage is the expression executable image -- meaning a structured file containing machine instructions and data, which can be loaded into a process's virtual memory and executed. See kernel (computers) image.

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 religion, an image is an idol or icon.

In philosophy, an image is a conception or idea.

In Comics, Image is a publisher of such characters as Spawn. See Image Comics.

See also: Wikipedia:Featured pictures