Editing Grayscale (section)

{{short description|Image where each pixel's intensity is shown only achromatic values of black, gray, and white}}
{{other uses|Grayscale (disambiguation)}}
{{More citations needed|date=March 2023}}
{{Use American English|date=July 2020}}
[[File:Grayscale 8bits palette sample image.png|thumb|right|Grayscale image of a parrot]]
{{Color depth}}

In [[digital photography]], [[computer-generated imagery]], and [[colorimetry]], a '''greyscale''' (more common in [[Commonwealth English]]) or '''grayscale''' (more common in [[American English]]) [[image]] is one in which the value of each [[pixel]] is a single [[sample (signal)|sample]] representing only an ''amount'' of [[light]]; that is, it carries only [[luminous intensity|intensity]] information. Grayscale images, are [[black-and-white]] or gray [[monochrome]], and composed exclusively of [[shades of gray]]. The [[contrast (vision)|contrast]] ranges from [[black]] at the weakest intensity to [[white]] at the strongest.<ref>{{cite book |last= Johnson |first= Stephen |date= 2006 |title= Stephen Johnson on Digital Photography |publisher= O'Reilly |isbn= 0-596-52370-X |url= https://books.google.com/books?id=0UVRXzF91gcC&q=grayscale+black-and-white-continuous-tone&pg=PA17}}</ref>

Grayscale images are distinct from one-bit bi-tonal black-and-white images, which, in the context of computer imaging, are images with only two [[color]]s: black and white (also called ''bilevel'' or ''[[binary image]]s''). Grayscale images have many shades of gray in between.

Grayscale images can be the result of measuring the intensity of light at each pixel according to a particular weighted combination of frequencies (or wavelengths), and in such cases they are [[monochromatic light|monochromatic]] proper when only a single [[frequency]] (in practice, a narrow band of frequencies) is captured. The frequencies can in principle be from anywhere in the [[electromagnetic spectrum]] (e.g. [[infrared]], [[visible spectrum|visible light]], [[ultraviolet]], etc.).

A [[colorimetry|colorimetric]] (or more specifically [[photometry (optics)|photometric]]) grayscale image is an image that has a defined grayscale [[colorspace]], which maps the stored numeric sample values to the achromatic channel of a standard colorspace, which itself is based on measured properties of [[Visual perception|human vision]].

If the original color image has no defined colorspace, or if the grayscale image is not intended to have the same human-perceived achromatic intensity as the color image, then there is no unique [[Map (mathematics)|mapping]] from such a color image to a grayscale image.