Parallel error diffusion method and apparatus

Claim 1

A method of reducing the rate at which an image formed by input pixels is error diffused, said image comprising at least one line of input pixels, said method comprising the steps of: (a) dividing the input pixels to be error diffused into at least two groups, said groups comprising different portions of the same at least one line of said image; (b) with a first one of the groups, performing a first series of sub-steps comprising: (b1) receiving the first group of input pixels and combining the first group of input pixels with a first group of previously calculated error diffusion data from neighbouring pixels to produce a first group of input corrected pixels; (b2) determining for each input corrected pixel of the first group a first display output value and associated error diffusion value to obtain a first group of display output data and a first group of error diffusion data, (b3) storing the first group of error diffusion data in a first storage means, (c) simultaneously with step (b), with a second one of the groups of input pixels, performing a second series of sub-steps comprising: (c1) error diffusing a second group of previously calculated input corrected pixels to obtain a second group of error diffusion data and a second group of display output data; (c2) receiving the second group of input pixels and combining the second group of input pixels with the second group of error diffusion data to obtain a second group of input corrected pixels; and (c3) storing the second group of input corrected pixels in a storage means.

Claim 2

A method of reducing the rate at which an image formed by input pixels is error diffused, said image comprising at least one line of input pixels, said method comprising the steps of: (a) dividing the input pixels to be error diffused into at least two groups, said groups comprising different portions of the same at least one line of said image; (b) with a first one of the groups, performing a first series of sub-steps comprising: (b1) receiving the first group of input pixels and combining the first group of input pixels with a first group of previously calculated error diffusion data from neighbouring pixels to produce a first group of input corrected pixels; (b2) determining for each input corrected pixel of the first group a first display output value and associated error diffusion value to obtain a first group of display output data and a first group of error diffusion data, (b3) storing the first group of error diffusion data in a first storage means, (c) simultaneously with step (b), with a second one of the groups of input pixels, performing a second series of sub-steps comprising: (c1) error diffusing a second group of previously calculated input corrected pixels to obtain a second group of error diffusion data and a second group of display output data; (c2) receiving the second group of input pixels and combining the second group of input pixels with the second group of error diffusion data to obtain a second group of input corrected pixels; and (c3) storing the second group of input corrected pixels in a storage means.