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In computing, a grayscale or greyscale digital image is an image in which the value of each pixel is a single sample. Displayed images of this sort are typically composed of shades of gray, varying from black at the weakest intensity to white at the strongest, though in principle the samples could be displayed as shades of any color, or even coded with various colors for different intensities. Grayscale images are distinct from black-and-white images, which in the context of computer imaging are images with only two colors, black and white; grayscale images have many shades of gray in between. In most contexts other than digital imaging, however, the term "black and white" is used in place of "grayscale"; for example, photography in shades of gray is typically called "black-and-white photography". The term monochromatic in some digital imaging contexts is synonymous with grayscale, and in some contexts synonymous with black-and-white.

Grayscale images are often the result of measuring the intensity of light at each pixel in a sigle band of the electromagnetic spectrum (e.g. visible light).

Grayscale images intended for visual display are typically stored with and 8 bits per sample, which allows 256 intensities (i.e., shades of gray) to be recorded, typically on a non-linear scale. The accuracy provided by this format is barely sufficient to avoid visible banding artifacts, but very convenient for programming. Technical uses (e.g. in medical imagingMedical imaging is the process by which physicians evaluate an area of the subject's body that is not normally visible. Medical imaging may be "clinical", seeking to diagnose and examine disease in specific human patients see pathology). Alternatively, it or remote sensingIn the broadest sense, remote sensing is the measurement or acquisition of information of an object or phenomenon, by a recording device that is not in physical or intimate contact with the object. It is the utilization at a distance (as from aircraft, sp applications) often require more levels, to make full use of the sensorA sensor is a device that detects, or senses a signal or physical condition. Most sensors are electrical or electronic, although other types exist. A sensor is a type of transducer. Sensors are either direct indicating (e. a mercury thermometer or electri accuracy (typically 10 or 12 bits per sample) and to guard against roundoff errors in computations. Sixteen bits per sample (65536 levels) appears to be a popular choice for such uses.

See also

• binary imageA binary image is a digital image that has only two possible values for each pixel. Binary images are also called bi-level or two-level''. The names black-and-white B&W monochrome or monochromatic are often used for this concept, but may also designate an
• false-color imageA false-color or pseudo-color image is a color image derived from a grayscale one by mapping each pixel value to a color according to a table or function. A familiar example is the encoding of altitude in physical relief maps, where negative values (below
• morphological image processingA collection of techniques for digital image processing based on Mathematical morphology. Since these techniques rely only on the relative ordering of pixel values, not on their numerical values, they are especially suited to the processing of binary imag