Editing Color histogram (section)

{{Short description|Representation of the distribution of colors in an image}}
{{distinguish|Image histogram}}
{{tone|date=October 2016}}
In [[image processing]] and [[photography]], a '''color histogram''' is a representation of the distribution of colors in an [[image]]. For digital images, a color histogram represents the number of [[pixel]]s that have colors in each of a fixed list of color ranges that span the image's [[color space]] (the set of all possible colors).

A color histogram can be built for any kind of color space, although the term is more often used for three-dimensional spaces such as [[RGB color space|RGB]] or [[HSV color space|HSV]].  For [[monochromatic image]]s, the term '''intensity histogram''' may be used instead.  For multi-spectral images, where each pixel is represented by an arbitrary number of measurements (for example, beyond the three measurements in RGB), a color histogram is ''N''-dimensional, with N being the number of measurements taken. Each measurement has its own wavelength range of the light spectrum, some of which may be outside the visible spectrum.

If the set of possible color values is sufficiently small, each of those colors may be placed on a range by itself; then the histogram is merely the count of pixels that have each possible color.  Most often, the space is divided into an appropriate number of ranges, often arranged as a regular grid, each containing many similar color values. A color histogram may also be represented and displayed as a smooth [[Function (mathematics)|function]] defined over the color space that approximates the pixel counts.

Like other kinds of [[histogram]]s, a color histogram is a [[statistic]] that can be viewed as an approximation of an underlying continuous [[Frequency distribution|distribution]] of color values.