Apparatus and method for generating void and cluster dither templates

Claim 1

An apparatus comprising: means for storing a binary bit pattern having M rows and N columns comprising first type bit elements and second type bit elements, wherein the type bit element of greatest number in said pattern is a majority type element, and the type bit element of least number in said pattern array is a minority type element; means for storing a dither template having M rows and N columns of integer threshold values in a template memory device having corresponding M rows and N columns of element locations; means for iteratively selecting a minority type element from said corresponding location from said pattern, said minority type element at said corresponding location selected in relation to neighboring minority type elements according to a first spatial characteristic, said means for iteratively selecting a minority type element further comprising: means for replacing said minority type element at said corresponding memory location with a majority type element to provide a second pattern array, and concurrently assigning a threshold value to a corresponding element location of said template memory; and means for iteratively selecting a majority type element from said pattern, said majority type element selected in relation to neighboring minority type elements according to a second, different spatial characteristic, said means for iteratively selecting a majority type element further comprising: means for replacing said majority type element at said corresponding pattern location with a minority type element to provide a third modified pattern, and concurrently assigning a threshold value to a corresponding element location of said template memory.

Claim 2

An apparatus comprising: a dithering system responsive to input image pixels from an input device having a first plurality of representation levels, including a memory for storing a dither template comprising an M by N array of elements representing a uniform distribution of integer threshold values having homogeneous attributes; means, responsive to said first plurality of representation levels, a second plurality of representation levels of an output device, and to said threshold values of said dither template, for providing a normalized dither matrix comprising normalized threshold values; means for combining said input image pixel representation levels to said normalized threshold values to provide summation signals; quantizer means for mapping said summation signals to said second plurality of representation levels to provide output pixels; and means for storing said output pixels.

Claim 12

A method comprising the steps of: a. storing in a memory device a pattern having M rows and N columns of locations, said pattern comprising a binary pattern of first type bit elements and second type bit elements, wherein said type bit element of greatest number in said pattern is a majority type element, and said type bit element of least number in said pattern is a minority type element; and b. iteratively selecting and moving said minority type elements and said majority type elements in said memory device between memory locations, wherein said minority type element location in memory is selected in relation to neighboring minority type elements according to a first spatial characteristic and said majority type element location in memory is selected in relation to neighboring minority type elements according to a second, different spatial characteristic; and repeating said step of iteratively selecting and moving until said minority type elements and majority type elements are uniformly distributed at pattern locations in said memory device to provide a modified pattern having homogeneous attributes.