Multi-level semi-vector error diffusion

Claim 3

The system of claim 1 , wherein the sum of the first and second separation pixels is given by: S = Round  { ( k - 1 )  [ i c + i m ] L } wherein i c is the first separation pixel and i m is the second separation pixel.

Claim 4

The system of claim 2 , wherein the k levels for the multi-level output values for the first and second separation pixels are given by jL/(k−1) for j=0 to k−1.

Claim 5

The system of claim 1 , wherein the second diffusion processor further includes a correction circuit for determining a correction term to be added to the multi-level output value for the third separation pixel, wherein the correction term is given by γ[ O C +O M −i C −i M ] where γ is between 0 and 1; O C is the multi-level output value for the first separation pixel; O M is the multi-level output value for the second separation pixel; i c is the first separation pixel and i m is the second separation pixel.

Claim 6

The system of claim 1 , wherein the first and second separations are cyan and magenta and the third separation is yellow.

Claim 9

The system of claim 1 , further comprising: a third diffusion processor, the third diffusion processor receiving a fourth separation pixel from a fourth color separation and generating a multi-level output value for the fourth separation pixel; and a separation adjustment processor generating one of the first, second and third separation pixels by subtracting a difference between the multi-level output value for the fourth separation pixel and the value of the fourth separation pixel from a separation pixel in one of the first, second and third separations.

Claim 10

A multi-level error diffusion method, comprising the steps of: receiving color image data comprising a plurality of color separations, each color separation including an array of separation pixels, each separation pixel having one of L values; generating a sum S of a first separation pixel and a second separation pixel, the first separation pixel being from a first color separation and the second separation pixel from a second color separation; generating a difference D between the first and second separation pixels; deriving a first multi-level output value for the first separation pixel and a second multi-level output value for the second separation pixel from the sum S and the difference D, the first and second multi-level output values each being one of k values wherein 1≦k≦L; and generating a third multi-level output value for a third separation pixel from a third color separation within the color image data.

Claim 11

A multi-level error diffusion method, comprising the steps of: receiving color image data comprising a plurality of color separations, each color separation including an array of separation pixels, each separation pixel having one of L values; generating a sum S of a first separation pixel and a second separation pixel, the first separation pixel being from a first color separation and the second separation pixel from a second color separation; generating a difference D between the first and second separation pixels; deriving a first multi-level output value for the first separation pixel and a second multi-level output value for the second separation pixel from the sum S and the difference D, the first and second multi-level output values each being one of k values wherein 1≦k≦L; and generating a third multi-level output value for a third separation pixel from a third color separation within the color image data.

Claim 12

The method of claim 8 , further comprising the steps of: generating a fourth multi-level output value for a fourth separation pixel from a fourth color separation within the color image; and subtracting a difference between the fourth multi-level output value and the value of the fourth separation pixel from at least one separation pixel in one of the first, second and third color separations.

Claim 13

The method of claim 8 , further comprising the steps of: generating an error value as a function of a difference between the first multi-level output value and the value of the first separation pixel; and subtracting the error value from a separation pixel in first color separation.

Claim 14

The method of claim 8 , wherein the sum S is given by: S = Round  { ( k - 1 )  [ i c + i m ] L } wherein i c is the first separation pixel and i m is the second separation pixel.

Claim 15

The method of claim 11 , wherein the k values for the first and second multi-level output values are given by jL/(k−1) for j=0 to k−1.

Claim 16

The method of claim 8 , wherein the step of generating a third multi-level output value further comprises adding a correction term the third multi-level output value, wherein the correction term is given by γ[ O C +O M −i C i M ] where γ is between 0 and 1; O C is the first multi-level output value; O M is the second multi-level output value; i c is the first separation pixel and i m is the second separation pixel.