Color is made of primary colors. Digital images are made of pixels. Pixels are made of combinations of primary colors. A channel in this context is the grayscale image of the same size as a color image, made of the proportion each primary color has in each pixel in the color image. Color is an important part of the visual arts. ... Primary color - Wikipedia /**/ @import /skins/monobook/IE50Fixes. ... A pixel (a contraction of picture element) is one of the many tiny dots that make up the representation of a picture in a computers memory. ...

In the digital realm, there can be any number of conventional primary colors making up an image; a channel in this case is extended to be the grayscale image based on any such conventional primary color. By extension, a channel is any grayscale image the same size with the "proper" image, and associated with it.

It's important to understand that the channels are a conventional term used to refer to a certain component of an image. In reality, any image format can use any algorithm internally to store images. For instance, GIF images actually store all components in one indexed color, per pixel. However, regardless of how a specific format stores the images, discrete color channels can always be determined, as long as a final color image can be rendered.

Uniform Channel Size

A 24-bit RGB image

The RED channel of the original RGB image

The GREEN channel of the original RGB image

The BLUE channel of the original RGB image

A 32-bit CMYK image

The CYAN channel of the original CMYK image

The MAGENTA channel of the original CMYK image

The YELLOW channel of the original CMYK image

The BLACK channel of the original CMYK image

An RGB image has three channels: red, green, and blue. If the CMYK image is 24-bit (the industy standard as of 2005), each channel has 8 bits, for red, green, and blue -- in other words, the image is composed of three grayscale images, where each grayscale image can store discreet pixels with conventional brightness intensities between 0 and 255. The RGB color model utilizes the additive model in which red, green, and blue light are combined in various ways to create other colors. ...

If the RGB image is 48-bit (very high quality), each channel is made of 16-bit grayscale images.

A CMYK image has four channels: cyan, magenta, yellow, and black. A 32-bit CMYK image (the industry standard as of 2005) is made of four 8-bit channels, one for cyan, one for magenta, one for yellow, and one for black. 64-bit storage for CMYK images (16-bit per channel) is not common, given the fact that CMYK is usually device-dependent, whereas RGB is the generic standard for device-independent storage. Cyan, magenta, yellow, and key (black) CMYK (or sometimes YMCK) is a subtractive color model used in color printing. ...

Optimized Channel Sizes

Images use very much digital "space". The huge majority of images/photographs being taken, generated, processed and/or reproduced are intended for human consumers. Given these two assumptions, scientists focused on saving digital space/bandwidth by creating image formats which yield good compromises between space usage and presentation. The most basic result of these studies is compressing the blue channel disproportionately more than the others, and compressing the green channel somewhere between red and blue. This type of "preferential" compression is the result of studies which show that the human retina actually uses the red channel to distinguish detail, along with the green channel in a lesser measure, and uses the blue channel for background or environmental information. Human eye cross-sectional view. ...