Quantization (image processing): Difference between revisions

Revision as of 03:35, 13 March 2006

Revision as of 03:38, 13 March 2006

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'''Quantization''', involved in [[image processing]]. Quantization techniques generally compress by compressing a range of values to a single quantum value. By reducing the number of discrete symbols in a given stream, the stream becomes more compressible. For example seeking to reduce the number of colors required to represent an [[image]]. Another widely used example -— [[DCT]] data quantization in [[JPEG]] and [[DWT]] data quantization in [[JPEG 2000]].

== Quantization in file formats ==

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The infinite number of colors available through the lens of a camera is impossible to display on a computer screen. Since a computer can display only a finite number of colors, quantization is always necessary.

Many early computers were limited in the number of colors they could display at one time --— commonly 16 (and later 256) colours. Modern computers can now display millions of colours at once, far more than can be distinguished by the human eye.

Most quantization algorithms allow you to set exactly how many colors you want to use. With the few colors available on early computers, different quantization algorithms produced very different-looking output images. As a result, a lot of time was spent on writing sophisticated algorithms to be more lifelike. Nowadays almost every algorithm produces an output indistinguishable from the view through the camera lens.

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For example, using &minus;415−415 (the DC coefficient) and rounding to the nearest integer

:<math>