Tone dependent plane dependent error diffusion halftoning

Claim 3

The method of claim 1 , wherein performing tone dependent error diffusion with a plurality of colors correlated comprises: performing error diffusion with the plurality of colors correlated to determine whether to print a dot of a first color ink, a dot of a second color ink, or no dot in approximately one pixel position; performing tone dependent error diffusion with the plurality of colors correlated to determine to print a dot of a first color ink, a dot of a second color ink, or no dot in approximately one pixel position.

Claim 4

The method of claim 2 , wherein performing error diffusion and performing tone dependent error diffusion comprises: (a) determining a tone in the pixel to be reproduced using at least two including the first color and the second color; (b) identifying a tone of the first color in the pixel to be reproduced; (c) identifying a tone of the second color in the pixel to be reproduced; (d) summing the tone of the first color and the tone of the second color to generate an input sum; (e) determining whether the input sum is greater than the full intensity threshold for the pixel and, if so, printing a dot of either the first color the second color; (f) generating a modified input sum by subtracting the full intensity threshold from the input sum if a dot of one of the first color or the second color was printed; (g) determining the tone dependent threshold level based on the modified input sum; and (h) determining whether to print a dot of the first color ink or the second color ink based on the tone dependent threshold level.

Claim 5

The method of claim 3 wherein the tone of the first color and a tone of the second color each has 256 levels ranging between 0 to 255, and wherein the full intensity threshold is at least 255.

Claim 6

The method of claim 3 wherein if it is determined in step (e) that the input sum is less than the full intensity threshold for the pixel, the tone dependent threshold level is determined based on the input sum.

Claim 7

The method of claim 3 , further comprising: accumulating the first error value signifying an error in the tone between printed dots of the first color in nearby pixels and the tone of the first color in the pixel; and accumulating a second error value signifying on error in the tone between printed dots of the second color in the nearby pixels and the tone of the second color in the pixel; wherein determining whether the input sum is greater than the full intensity threshold for the pixel and, if so, printing a dot of either the first color or the second color further comprises: determining whether the tone of the first color plus the first error value is greater than the tone of the second color plus the second error value and, if so, printing the dot of the first color ink and, if not, printing the dot of the second color ink.

Claim 8

The method of claim 3 , wherein determining the tone dependent threshold level based on the modified input sum comprises indexing at least one look-up table with the modified input sum and outputting by the at least one look-up table a threshold level, the method further comprising: generating a modified first error value and a modified second error value based on the first error value and the second error value and whether a dot of the first color ink or the second color ink has already been printed; summing the tone of the first color, the modified first error value, the tone of the second color, and the modified second error value to produce a modified total value sum; and determining whether the modified total value sum is greater than the threshold level and if so, printing a dot of the first color ink or the second color ink.

Claim 9

The method of claim 7 , further comprising raising the threshold level prior to determining whether the modified total value sum value is greater than the threshold level if a dot of the first color ink or the second color ink has already been printed.

Claim 10

The method of claim 7 , wherein determining whether the in modified total value sum is greater than the threshold and if so, printing a dot of the first color ink or the second color ink further comprises determining whether the tone of the first color plus the modified first error value is greater than the tone of the second color plus the modified second error value and, if so, printing a dot of the first color ink and if not, printing a dot of the second color ink.

Claim 11

The method of claim 3 , further comprising: (i) determining at least two tone dependent error weightings based on the modified input sum; (j) determining a first dispersion error value for the first color and a second dispersion error value for the second color; (k) accumulating a first error value signifying an error in the tone between printed dots of the first color in nearby pixels and the tone of the first color in the pixel; (l) accumulating a second error value signifying an error in the tone between printed dots of the second color in the nearby pixels and the tone of the second color in the pixel; (m) generating a first dispersion error value and a second dispersion error value based on the first error value and the second error value and the tone of the first color and the tone of the second color and whether a dot of the first color ink or the second color in has been printed; and (n) diffusing the first dispersion error value and the second dispersion error value using the at least two tone dependent error weightings.

Claim 12

The method of claim 10 , wherein four error weightings are determined based on the modified input sum by indexing at least one look-up table and the first dispersion error value and the second dispersion error value are diffused using the four error weightings.

Claim 13

The method of claim 1 , wherein the plurality of colors comprises the first color, the second color, and at least a third color, the method further comprising: prioritizing the first color ink, the second color ink, and the at least a third color ink when determining what color ink dot to print.

Claim 14

The method of claim 1 , wherein the method is performed by printing system comprising an inkjet printer and a computer.

Claim 15

The method of claim 1 , wherein no dots are printed if neither the combined tone from the first color and the second color is greater than the full intensity threshold for the pixel nor the combined tone and accumulated error from the first color and the second color is greater than the tone dependent threshold level.

Claim 16

The method of claim 1 , wherein two dots are printed if the combined tone from the first color and the second color is greater than the full intensity threshold for the pixel and the combined tone and the accumulated error from the first color and the second color is greater than the tone dependent threshold level.

Claim 17

A printing system including a printer and a computer, the printing system performing a color halftone method which correlates multiple color planes to reduce a likelihood that printed dots of any color will be unintentionally overlapping and to provide printed dots with uniform placement, the method performed by the system comprising: performing tone dependent error diffusion with a plurality of colors correlated to determine whether to print no dots, whether to print one dot of either a first color ink or a second color ink, and whether to print two dots including one dot of the first color ink and one dot of the second color ink in approximately the same position: and correlating printing of dots of a first color with dots of a second color to reduce a likelihood that printed dots of the first color will unintentionally overlap printed dots of the second color, wherein two dots are printed if a combined tone from the first color and the second color is greater than an intensity threshold for the pixel or the combined tone and the accumulated error from the first color and the second color is greater than the tone dependent threshold, wherein one dot is printed if either the combined tone from the first color and the second color is greater than the intensity thershold for the pixel or the combined tone and the accumulated error from the first color and the second color is greater than the tone dependent threshold, and wherein no dots are printed if neither the combined tone from the first color and the second color is greater than the intensity threshold for the pixel nor the combined tone and the accumulated error from the first color and the second color is greater than the tone dependent threshold.

Claim 18

A printing system including a printer and a computer, the printing system performing a color halftone method which correlates multiple color planes to reduce a likelihood that printed dots of any color will be unintentionally overlapping and to provide printed dots with uniform placement, the method performed by the system comprising: performing tone dependent error diffusion with a plurality of colors correlated to determine whether to print no dots, whether to print one dot of either a first color ink or a second color ink, and whether to print two dots including one dot of the first color ink and one dot of the second color ink in approximately the same position: and correlating printing of dots of a first color with dots of a second color to reduce a likelihood that printed dots of the first color will unintentionally overlap printed dots of the second color, wherein two dots are printed if a combined tone from the first color and the second color is greater than an intensity threshold for the pixel or the combined tone and the accumulated error from the first color and the second color is greater than the tone dependent threshold, wherein one dot is printed if either the combined tone from the first color and the second color is greater than the intensity thershold for the pixel or the combined tone and the accumulated error from the first color and the second color is greater than the tone dependent threshold, and wherein no dots are printed if neither the combined tone from the first color and the second color is greater than the intensity threshold for the pixel nor the combined tone and the accumulated error from the first color and the second color is greater than the tone dependent threshold.

Claim 19

The system of claim 16 wherein the printer is an inkjet printer.

Claim 20

The system of claim 16 further comprising a separate print cartridge for each color ink to be printed.

Claim 21

The system of claim 16 , further comprising a print cartridge which prints black ink and at least one print cartridge which prints multiple color of ink.

Claim 24

The method as set forth in claim 20 , wherein the tone dependent error weightings are used to diffuse the final accumulated errors for each color plane.