A visual comparison is to compare two or more things by eye. This might be done by placing them side by side; by overlaying them; by alternating an image or by presenting each image to a separate eye. Such comparisons are the first stage in a child's development of an understanding of geometry and measurement, before they move to an understanding of measuring devices such as a ruler. People with sufficient control over the

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...

of their eyeballs (e.g. those who can easily view random-dot

stereograms Stereoscopy, also called stereoscopics or stereo imaging, is a technique for creating or enhancing the illusion of depth in an image by means of stereopsis for binocular vision. The word ''stereoscopy'' derives . Any stereoscopic image is ...

) can hold up two paper printouts and go cross-eyed to superimpose them. This invokes deep, fast, built-in image comparison wetware (the same machinery responsible for

depth perception Depth perception is the ability to perceive distance to objects in the world using the visual system and visual perception. It is a major factor in perceiving the world in three dimensions. Depth sensation is the corresponding term for non-hum ...

) and differences stand out almost immediately. This technique is good for finding edits in graphical images, or for comparing an image with a compressed version to spot artefacts. Visual comparison with a standard chart or reference is often used as a means of measuring complex phenomena such as the

weather Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloud cover, cloudy. On Earth, most weather phenomena occur in the lowest layer of the planet's atmo ...

, sea states or the roughness of a river. A

colour chart A color chart or color reference card is a flat, physical object that has many different color samples present. They can be available as a single-page chart, or in the form of swatchbooks or color-matching fans. Typically there are two differ ...

is used for this purpose in many contexts such as

chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...

cosmetics Cosmetics are substances that are intended for application to the body for cleansing, beautifying, promoting attractiveness, or altering appearance. They are mixtures of chemical compounds derived from either Natural product, natural source ...

medical test A medical test is a medical procedure performed to detect, diagnose, or monitor diseases, disease processes, susceptibility, or to determine a course of treatment. Medical tests such as, physical and visual exams, diagnostic imaging, genetic ...

ing and

photography Photography is the visual arts, art, application, and practice of creating images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is empl ...

. Comparison by eye may also be used as a source of amusement or

intelligence testing An intelligence quotient (IQ) is a total score derived from a set of standardized tests or subtests designed to assess human intelligence. Originally, IQ was a score obtained by dividing a person's mental age score, obtained by administering ...

, as in the popular puzzle of

spot the difference Spot the difference is a type of puzzle where players must find a set number of differences between two otherwise similar images. Description Spot the difference games are found in various media including activity books for children, newspap ...

. In

policing The police are a constituted body of people empowered by a state with the aim of enforcing the law and protecting the public order as well as the public itself. This commonly includes ensuring the safety, health, and possessions of citizen ...

, the technique is used for analysis of

fingerprint A fingerprint is an impression left by the friction ridges of a human finger. The recovery of partial fingerprints from a crime scene is an important method of forensic science. Moisture and grease on a finger result in fingerprints on surfa ...

s and identity parades. Visual comparison task can be simplified by using a computer software that automatically aligns a pair of images based on common visual features present in the two images.

Computer jargon

A visual diff or vdiff finds differences between two files by eyeball search. The term optical diff has also been reported, and is sometimes more specifically used for the act of superimposing two nearly identical printouts on one another and holding them up to a light to spot differences. Though this method is poor for detecting omissions in the ‘rear’ file, it can also be used with printouts of graphics, a claim few

diff In computing, the utility diff is a data comparison tool that computes and displays the differences between the contents of files. Unlike edit distance notions used for other purposes, diff is line-oriented rather than character-oriented, but i ...

programs can make.''

Jargon File The Jargon File is a glossary and usage dictionary of slang used by computer programmers. The original Jargon File was a collection of terms from technical cultures such as the MIT Computer Science and Artificial Intelligence Laboratory, MIT AI Lab ...

'', version 4.4.6, 25 Oct 2003

References

{{Improve categories, date=January 2024 Vision Data differencing

Computer jargon

See also

References