A bitmap may also represent a colored image, in which case more than one bit will be used to represent each pixel . Computer graphics that treat images as collections of dots rather than as shapes, or objects, may be described as bitmapped graphics or raster graphics . Contrast with vector graphics . In a digital image , a pixel whose value is undefined. In computer storage of quantized digital images, some special numeric value is assigned to the blanked pixels, so that they may be recognized as undefined and given whatever special treatment is required.
Spatial differences appear to move back and forth, while intensity differences pulsate.
When the switching rate, duty cycle and transfer functions of the displays are controllable by the user, blinking is a powerful tool for assessing subtle but systematic differences between images, e.g. those due to moving or variable objects in crowded fields, or to subtle artifacts in image formation. A measure of the intensity of a region of the sky, based on the temperature of a black body that would emit radiation of the observed intensity at the given observing frequency. Frequently computed in radio astronomy using the Rayleigh-Jeans approximation, in which case it is directly proportional to the intensity per unit area. For thermal emission mechanisms, it may correspond to a physical temperature in an emitting region. If the frequency channels are narrow enough, one can expand the u-v coverage considerably with immunity to bandwidth smearing .