Color image
Encyclopedia
A color image is a digital image
that includes color
information for each pixel
.
For visually acceptable results, it is necessary (and almost sufficient) to provide three samples (color channels) for each pixel, which are interpreted as coordinates in some color space. The RGB color space is commonly used in computer displays, but other spaces such as YCbCr
, HSV, and are often used in other contexts.
, a two-dimensional array of small integer triplets; or (rarely) as three separate raster maps, one for each channel.
Eight bits per sample (24 bits per pixel) seem adequate for most uses, but faint banding artifacts may still be visible in some smoothly varying images, especially those subject to processing
. Particularly demanding applications may use 10 bits per sample or more.
On the other hand, some widely used image file formats and graphics cards may use only 8 bits per pixel, i.e., only 256 different colors, or 2–3 bits per channel. Converting continuous-tone images like photographs to such formats requires dithering and yields rather grainy and fuzzy results.
Graphics cards that support 16 bits per pixel provide 65536 distinct colors, or 5–6 bits per channel. This resolution seems satisfactory for non-professional uses, even without dithering.
Digital image
A digital image is a numeric representation of a two-dimensional image. Depending on whether or not the image resolution is fixed, it may be of vector or raster type...
that includes color
Color
Color or colour is the visual perceptual property corresponding in humans to the categories called red, green, blue and others. Color derives from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors...
information for each pixel
Pixel
In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
.
For visually acceptable results, it is necessary (and almost sufficient) to provide three samples (color channels) for each pixel, which are interpreted as coordinates in some color space. The RGB color space is commonly used in computer displays, but other spaces such as YCbCr
YCbCr
YCbCr or Y′CbCr, sometimes written or , is a family of color spaces used as a part of the color image pipeline in video and digital photography systems. Y′ is the luma component and CB and CR are the blue-difference and red-difference chroma components...
, HSV, and are often used in other contexts.
Color image representation
A color image is usually stored in memory as a raster mapRaster graphics
In computer graphics, a raster graphics image, or bitmap, is a data structure representing a generally rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other display medium...
, a two-dimensional array of small integer triplets; or (rarely) as three separate raster maps, one for each channel.
Eight bits per sample (24 bits per pixel) seem adequate for most uses, but faint banding artifacts may still be visible in some smoothly varying images, especially those subject to processing
Digital image processing
Digital image processing is the use of computer algorithms to perform image processing on digital images. As a subcategory or field of digital signal processing, digital image processing has many advantages over analog image processing...
. Particularly demanding applications may use 10 bits per sample or more.
On the other hand, some widely used image file formats and graphics cards may use only 8 bits per pixel, i.e., only 256 different colors, or 2–3 bits per channel. Converting continuous-tone images like photographs to such formats requires dithering and yields rather grainy and fuzzy results.
Graphics cards that support 16 bits per pixel provide 65536 distinct colors, or 5–6 bits per channel. This resolution seems satisfactory for non-professional uses, even without dithering.