Generating threshold values in a dither matrix

1. A method, comprising:

a printer generating a dither matrix of threshold values; and

the printer filtering the threshold values in the dither matrix to generate a filtered dither matrix of filtered dither values by:

determining a region of dither values in the dither matrix that surrounds the value being considered, wherein the dither values in the determined region comprise one of dither values in a first portion of the region within the dither matrix or a wrap around dither value in a second portion of the region that extends beyond the dither matrix;

using an offset value to determine one wrap around dither value, wherein repeated instances of the dither matrix are designed to be applied to an image by forming a tile pattern of the repeated instances of the matrix over the image pattern, and wherein the repeated instances of the matrix in the tile pattern are offset in one direction by the offset value; and

performing an operation on the determined dither values in the region to determine a filtered value for the dither value being considered.

2. The method of claim 1 , wherein the operation on the determined surrounding dither values comprises determining a weighted average of the dither values in the region surrounding the dither value being considered.

3. The method of claim 2 , where said weighted average is determined by a filtering operation such as convolution.

4. The method of claim 3 , wherein the region forms one of a rectangle, square or circular shape.

5. The method of claim 1 , wherein the region forms a geometric shape and the value being considered lies within the region.

6. The method of claim 1 , wherein the value being considered lies in the center of said region.

7. The method of claim 6 , wherein the offset value is approximately one half of n.

8. The method of claim 6 , wherein said offset value is a positive or negative integer.

9. The method of claim 1 , wherein values in the matrix have an (x, y) coordinate position in the matrix such that 1≦x. ≦m and 1≦y≦n, wherein the wrap around value has an (x, y) coordinate position in the second portion of the region such that 1>x or x>m or 1>y or y>n, wherein the (x′, y′) coordinates in dither matrix providing the wrap around value are calculated by performing an operation on the (x, y) coordinates of the wrap around value using the offset value to determine coordinates (x′, y′) within the matrix providing the dither value for the wrap around value.

10. The method of claim 9 , wherein the offset value is used to determine the y′ coordinate in the dither matrix but not the x′ coordinate in the dither matrix.

11. The method of claim 10 , wherein the value m is used to determine the x′ coordinate.

12. The method of claim 9 , wherein performing the operation on the (x, y) coordinates to determine the (x′, y′) coordinates comprises:

x′=x mod m, wherein 0<x′≦m; and

y′=y″ mod n, where t=(x−x′)/m, and where y″=y−(t*offset value).

13. The method of claim 12 , further comprising:

if 0<x≦m, then x′=x; and

if 0<y≦n, then y′=y.

14. The article of manufacture of claim 9 , wherein values in the matrix have an (x, y) coordinate position in the matrix such that 1≦x≦m and 1≦y≦n, wherein the wrap around value has an (x, y) coordinate position in the second portion of the region such that 1>x or x>m or 1>y or y>n, wherein the (x′, y′) coordinates in dither matrix providing the wrap around value are calculated by performing an operation on the (x, y) coordinates of the wrap around value using the offset value to determine coordinates (x′, y′) within the matrix providing the dither value for the wrap around value.

15. The system of claim 1 , wherein values in the matrix have an (x, y) coordinate position in the matrix such that 1≦x≦m and 1≦y≦n, wherein the wrap around value has an (x, y) coordinate position in the second portion of the region such that 1>x or x>m or 1>y or y>n, wherein the (x′, y′) coordinates in dither matrix providing the wrap around value are calculated by performing an operation on the (x, y) coordinates of the wrap around value using the offset value to determine coordinates (x′, y′) within the matrix providing the dither value for the wrap around value.

16. The system of claim 15 , wherein the offset value is used to determine the y′ coordinate in the dither matrix but not the x′ coordinate in the dither matrix.

17. The system of claim 16 , wherein the value m is used to determine the x′ coordinate.

18. The article of manufacture of claim 17 , wherein the offset value is used to determine the y′ coordinate in the dither matrix but not the x′ coordinate in the dither matrix.

19. A system, comprising:

an integrated circuit, including:

a matrix generator for generating a dither matrix of threshold values; and

a dither matrix filter for filtering the threshold values in the dither matrix to generate a filtered dither matrix of filtered dither values by:

determining a region of dither values in the dither matrix that surrounds the value being considered, wherein the dither values in the determined region comprise one of dither values in a first portion of the region within the dither matrix or a wrap around dither value in a second portion of the region that extends beyond the dither matrix;

using an offset value to determine one wrap around dither value, wherein repeated instances of the dither matrix are designed to be applied to an image by forming a tile pattern of the repeated instances of the matrix over the image pattern, and wherein the repeated instances of the matrix in the tile pattern are offset in one direction by the offset value; and

performing an operation on the determined dither values in the region to determine a filtered value for the dither value being considered.

20. An article of manufacture including code, is stored on a computer readable medium, wherein the code, when executed by a processor causes the processor to perform:

generating a dither matrix of threshold values; and

filtering the threshold values in the dither matrix to generate a filtered dither matrix of filtered dither values by:

determining a region of dither values in the dither matrix that surrounds the value being considered, wherein the dither values in the determined region comprise one of dither values in a first portion of the region within the dither matrix or a wrap around dither value in a second portion of the region that extends beyond the dither matrix;

using an offset value to determine one wrap around dither value, wherein repeated instances of the dither matrix are designed to be applied to an image by forming a tile pattern of the repeated instances of the matrix over the image pattern, and wherein the repeated instances of the matrix in the tile pattern are offset in one direction by the offset value; and

performing an operation on the determined dither values in the region to determine a filtered value for the dither value being considered.