A digital image
a gray-scale image can be represented as matrix of 'grayness' values
each dot in the matrix is called a pixel (picture element)
each pixel has a grayness value, typically 0..255
displays or printers adjust the amount of light, or ink, for grayness
(B&W uses just one bit, i.e., 0 or 1)
(color uses three values, Red, Green, Blue)
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