colour (redirected from complementary after-image)

colour

Aspect of any object that may be described in terms of hue, brightness, and saturation. It is associated with the visible wavelengths of electromagnetic radiation, which stimulate the sensor cells of the eye. Red light has the longest wavelengths, while blue has the shortest, with other colours such as orange, yellow, and green between. Hue refers to dominant wavelengths. Brightness refers to the intensity or degree of shading. Saturation pertains to purity, or the amount of white light mixed with a hue. The colours red, yellow, and blue, known as primary colours, can be combined in varying proportions to produce all other colours. Primary colours combined in equal proportions produce secondary colours. Two colours that combine to form white light are said to be complementary.

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colour (US), color

1. 

a. an attribute of things that results from the light they reflect, transmit, or emit in so far as this light causes a visual sensation that depends on its wavelengths

b. the aspect of visual perception by which an observer recognizes this attribute

c. the quality of the light producing this aspect of visual perception

d. (as modifier): colour vision

2. 

a. a colour, such as red or green, that possesses hue, as opposed to achromatic colours such as white or black

b. (as modifier): a colour television

3. 

a. the skin complexion of a person, esp as determined by his race

b. (as modifier): colour prejudice

4. the use of all the hues in painting as distinct from composition, form, and light and shade

5. the distinctive tone of a musical sound; timbre

6. Physics one of three characteristics of quarks, designated red, blue, or green, but having no relationship with the physical sensation

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(graphics)

colour - (US "color") Colours are usually represented as RGB triples in a digital image because this corresponds most closely to the electronic signals needed to drive a CRT. Several equivalent systems ("colour models") exist, e.g. HSB. A colour image may be stored as three separate images, one for each of red, green, and blue, or each pixel may encode the colour using separate bit-fields for each colour component, or each pixel may store a logical colour number which is looked up in a hardware colour palette to find the colour to display. Printers may use the CMYK or Pantone representations of colours as well as RGB.