Color Quantisation in Operating Systems
Introduction
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Colour Quantisation is the process of mapping colours from a source image to the nearest available colour in a display device’s limited palette.
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It becomes necessary in graphical OS environments when a display device cannot represent all colours present in an image.
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The source image is assumed to be a 24-bit bitmap with 8 bits each for red, green, and blue — the typical worst-case scenario for colour depth.
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The Colour Quantiser is the system component responsible for performing this mapping.
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Dithering is a related technique often applied alongside quantisation to simulate missing colours by spatially mixing available ones, improving overall reproduction quality.
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The term “Colour Quantisation” has a second meaning — calculating a reduced palette from an image that preserves colour detail.