Method and apparatus for pseudo-random noise generation based on

Abstract

A method and apparatus for dithering for color computer display systems includes the addition of a noise component to each of the color components of each pixel in a pseudo-random manner. The noise component is preferably different for each color component. Taking the image as a whole, the noise component repeats on a regular basis but is preferably selected so as not to repeat on adjacent pixels. The image is divided into squares of pixels and the same noise component is added to each of the same relative pixels from square to square. The preferred square of pixels is four pixels wide by four pixels high. The value of the noise component is chosen such that the most significant bit alternates both horizontally and vertically from pixel to pixel within the square of pixels. The other bits of the value of the noise component are preferably chosen such that the value of the noise component does not repeat within the square of pixels and such that a simplified hardware implementation is made possible by their selection. The resulting hardware implementation preferably consists of a number of exclusive-or gates tied together to produce the value of the noise component based on the least significant bits of the X and Y coordinates of each pixel. This hardware implementation is simple enough that it becomes economically practical to add a different noise component to each of the three color components of each pixel rather than the same noise component to all of the color components.