Threshold matrix generation method, threshold matrix generating apparatus, and recording medium

Claim 2

1 . A threshold matrix generation method of generating a threshold matrix which is compared with a grayscale original image in halftoning said original image, comprising the steps of: a) preparing a plurality of types of basic tiles each of which is an arrangement of elements in two rows and two columns consisting of two ON elements each representing existence of a dot and two OFF elements each representing absence of a dot, and arranging a plurality of basic tiles each of which is one of said plurality of types of basic tiles, in a matrix area where a threshold matrix is generated, in accordance with a prohibition condition for at least prohibiting an arrangement of only ON elements or OFF elements in an area of two rows and two columns, to acquire an element matrix representing an arrangement of dots in a gray level of 50%; b) setting a dot at arbitrary one element on a highlight dot pattern which is a set of ON elements in said element matrix; c) repeating a process of adding a new dot to an element on said highlight dot pattern, said new dot being farthest from existing dots on said highlight dot pattern, on the premise of spatial repetition of said threshold matrix in halftoning of an original image, or repeating said process in accordance with a predetermined condition, to determine a turn-on order in which dots are added to elements in accordance with increase in gray level on a highlight side; d) setting dots at all elements excluding arbitrary one element on a shadow dot pattern which is a set of OFF elements in said element matrix; e) repeating a process of removing a dot of an element on said shadow dot pattern, said dot being farthest from elements in each of which a dot is not set on said shadow dot pattern, on the premise of spatial repetition of said threshold matrix, to determine a turn-off order in which dots are removed from elements in accordance with decrease in gray level on a shadow side; and f) determining a threshold value of each element in said matrix area in accordance with said turn-on order and said turn-off order.

Claim 3

2 . The threshold matrix generation method according to claim 1 , wherein said plurality of types of basic tiles are two types of arrangements in each of which said two ON elements are arranged diagonally.

Claim 4

3 . The threshold matrix generation method according to claim 1 , wherein said two ON elements are arranged in a row direction or a column direction in each of said plurality of types of basic tiles.

Claim 5

4 . The threshold matrix generation method according to claim 1 , wherein said step a) comprises the steps of: a1) setting a basic tile of one type at arbitrary one tile position in said matrix area; a2) setting a new basic tile of said one type at a tile position which is farthest from basic tiles of said one type in accordance with said prohibition condition, on the premise of spatial repetition of said threshold matrix; and a3) repeating said step a2) by a predetermined number of times.

Claim 6

5 . The threshold matrix generation method according to claim 4 , wherein said step a) further comprises the steps of: a4) changing a type of a basic tile which is set at one tile position different from said arbitrary one tile position in said matrix area where said plurality of basic tiles are arranged, after said step a3); a5) changing a type of a basic tile which is set at a tile position farthest from basic tiles whose type has been changed, in accordance with said prohibition condition on the premise of spatial repetition of said threshold matrix; and a6) repeating said step a5) by a predetermined number of times.

Claim 7

6 . The threshold matrix generation method according to claim 4 , wherein the number of elements in at least one of a row direction and a column direction in said element matrix is a value which is different from a power of two.

Claim 8

7 . The threshold matrix generation method according to claim 1 , wherein said matrix area corresponds to one color component, and said steps a) to f) are performed in a matrix area of another color component which is different from said matrix area of said one color component, to generate a threshold matrix of said another color component which has a different size from a threshold matrix of said one color component.

Claim 9

8 . The threshold matrix generation method according to claim 1 , wherein resolutions in two directions which respectively corresponds to a row direction and a column direction in said matrix area, are different from each other in an image recording apparatus for recording a halftone image, which is generated by halftoning said original image, on an object, and a weighting coefficient for a distance in said row direction and a weighting coefficient for a distance in said column direction are different from each other in accordance with said resolutions in said two directions, when an element which is farthest from existing dots or an element which is farthest from elements where dots are not set is specified in each of said steps c) and e).

Claim 10

9 . The threshold matrix generation method according to claim 1 , wherein a plurality of dots having different sizes can be formed on an object in an image recording apparatus for recording a halftone image, which is generated by halftoning said original image, on said object, and said threshold matrix generation method further comprises the step of generating a plurality of sub-threshold values used for determination of size of a dot from said threshold value of said each element in said matrix area.

Claim 11

10 . The threshold matrix generation method according to claim 1 , wherein a halftone image generated by halftoning said original image is recorded on an object by ejecting fine droplets of ink from a plurality of outlets arranged in a predetermined arrangement direction, in an image recording apparatus for recording said halftone image on said object, each element group which is a group of elements arranged in one direction out of a row direction and a column direction in said element matrix includes at least one ON element and the other direction corresponds to said arrangement direction of said plurality of outlets, and said predetermined condition in said step c) is that one of numbers 1 to α in said turn-on order is assigned to one element in said each element group in said element matrix where the number of elements in said other direction in said element matrix is α.

Claim 12

11 . A threshold matrix generating apparatus for generating a threshold matrix which is compared with a grayscale original image in halftoning said original image, comprising: an element matrix acquisition part for preparing a plurality of types of basic tiles each of which is an arrangement of elements in two rows and two columns consisting of two ON elements each representing existence of a dot and two OFF elements each representing absence of a dot, and arranging a plurality of basic tiles each of which is one of said plurality of types of basic tiles, in a matrix area where a threshold matrix is generated, in accordance with a prohibition condition for at least prohibiting an arrangement of only ON elements or OFF elements in an area of two rows and two columns, to acquire an element matrix representing an arrangement of dots in a gray level of 50%; a turn-on order determining part for setting a dot at arbitrary one element on a highlight dot pattern which is a set of ON elements in said element matrix and thereafter, repeating a process of adding a new dot to an element on said highlight dot pattern, said new dot being farthest from existing dots on said highlight dot pattern, on the premise of spatial repetition of said threshold matrix in halftoning of an original image, or repeating said process in accordance with a predetermined condition, to determine a turn-on order in which dots are added to elements in accordance with increase in gray level on a highlight side; a turn-off order determining part for setting dots at all elements excluding arbitrary one element on a shadow dot pattern which is a set of OFF elements in said element matrix and thereafter, repeating a process of removing a dot of an element on said shadow dot pattern, said dot being farthest from elements in each of which a dot is not set on said shadow dot pattern, on the premise of spatial repetition of said threshold matrix, to determine a turn-off order in which dots are removed from elements in accordance with decrease in gray level on a shadow side; and a threshold value determining part for determining a threshold value of each element in said matrix area in accordance with said turn-on order and said turn-off order.

Claim 13

11 . A threshold matrix generating apparatus for generating a threshold matrix which is compared with a grayscale original image in halftoning said original image, comprising: an element matrix acquisition part for preparing a plurality of types of basic tiles each of which is an arrangement of elements in two rows and two columns consisting of two ON elements each representing existence of a dot and two OFF elements each representing absence of a dot, and arranging a plurality of basic tiles each of which is one of said plurality of types of basic tiles, in a matrix area where a threshold matrix is generated, in accordance with a prohibition condition for at least prohibiting an arrangement of only ON elements or OFF elements in an area of two rows and two columns, to acquire an element matrix representing an arrangement of dots in a gray level of 50%; a turn-on order determining part for setting a dot at arbitrary one element on a highlight dot pattern which is a set of ON elements in said element matrix and thereafter, repeating a process of adding a new dot to an element on said highlight dot pattern, said new dot being farthest from existing dots on said highlight dot pattern, on the premise of spatial repetition of said threshold matrix in halftoning of an original image, or repeating said process in accordance with a predetermined condition, to determine a turn-on order in which dots are added to elements in accordance with increase in gray level on a highlight side; a turn-off order determining part for setting dots at all elements excluding arbitrary one element on a shadow dot pattern which is a set of OFF elements in said element matrix and thereafter, repeating a process of removing a dot of an element on said shadow dot pattern, said dot being farthest from elements in each of which a dot is not set on said shadow dot pattern, on the premise of spatial repetition of said threshold matrix, to determine a turn-off order in which dots are removed from elements in accordance with decrease in gray level on a shadow side; and a threshold value determining part for determining a threshold value of each element in said matrix area in accordance with said turn-on order and said turn-off order.

Claim 14

12 . The threshold matrix generating apparatus according to claim 11 , wherein said plurality of types of basic tiles are two types of arrangements in each of which said two ON elements are arranged diagonally.

Claim 15

13 . The threshold matrix generating apparatus according to claim 11 , wherein said two ON elements are arranged in a row direction or a column direction in each of said plurality of types of basic tiles.

Claim 16

14 . The threshold matrix generating apparatus according to claim 11 , wherein said element matrix acquisition part executes the steps of: a1) setting a basic tile of one type at arbitrary one tile position in said matrix area; a2) setting a new basic tile of said one type at a tile position which is farthest from basic tiles of said one type in accordance with said prohibition condition, on the premise of spatial repetition of said threshold matrix; and a3) repeating said step a2) by a predetermined number of times.

Claim 17

15 . The threshold matrix generating apparatus according to claim 14 , wherein said element matrix acquisition part further executes the steps of: a4) changing a type of a basic tile which is set at one tile position different from said arbitrary one tile position in said matrix area where said plurality of basic tiles are arranged, after said step a3); a5) changing a type of a basic tile which is set at a tile position farthest from basic tiles whose type has been changed, in accordance with said prohibition condition on the premise of spatial repetition of said threshold matrix; and a6) repeating said step a5) by a predetermined number of times.

Claim 18

16 . The threshold matrix generating apparatus according to claim 14 , wherein the number of elements in at least one of a row direction and a column direction in said element matrix is a value which is different from a power of two.

Claim 19

17 . The threshold matrix generating apparatus according to claim 11 , wherein said matrix area corresponds to one color component, and said element matrix acquisition part, said turn-on order determining part, said turn-off order determining part, and said threshold value determining part generate a threshold matrix of another color component which has a different size from a threshold matrix of said one color component, in a matrix area of said another color component which is different from said matrix area of said one color component.

Claim 20

18 . The threshold matrix generating apparatus according to claim 11 , wherein resolutions in two directions which respectively corresponds to a row direction and a column direction in said matrix area, are different from each other in an image recording apparatus for recording a halftone image, which is generated by halftoning said original image, on an object, and a weighting coefficient for a distance in said row direction and a weighting coefficient for a distance in said column direction are different from each other in accordance with said resolutions in said two directions, when an element which is farthest from existing dots or an element which is farthest from elements where dots are not set is specified in each of said turn-on order determining part and said turn-off order determining part.

Claim 21

19 . The threshold matrix generating apparatus according to claim 11 , wherein a plurality of dots having different sizes can be formed on an object in an image recording apparatus for recording a halftone image, which is generated by halftoning said original image, on said object, and said threshold value determining part generates a plurality of sub-threshold values used for determination of size of a dot from said threshold value of said each element in said matrix area.

Claim 22

20 . The threshold matrix generating apparatus according to claim 11 , wherein a halftone image generated by halftoning said original image is recorded on an object by ejecting fine droplets of ink from a plurality of outlets arranged in a predetermined arrangement direction, in an image recording apparatus for recording said halftone image on said object, each element group which is a group of elements arranged in one direction out of a row direction and a column direction in said element matrix includes at least one ON element and the other direction corresponds to said arrangement direction of said plurality of outlets, and said predetermined condition in said turn-on order determining part is that one of numbers 1 to α in said turn-on order is assigned to one element in said each element group in said element matrix where the number of elements in said other direction in said element matrix is α.

Claim 23

21 . An electronic apparatus-readable recording medium in which data of a threshold matrix is recorded, said threshold matrix being compared with a grayscale original image in halftoning said original image, said data being generated by executing steps including the steps of: a) preparing a plurality of types of basic tiles each of which is an arrangement of elements in two rows and two columns consisting of two ON elements each representing existence of a dot and two OFF elements each representing absence of a dot, and arranging a plurality of basic tiles each of which is one of said plurality of types of basic tiles, in a matrix area where a threshold matrix is generated, in accordance with a prohibition condition for at least prohibiting an arrangement of only ON elements or OFF elements in an area of two rows and two columns, to acquire an element matrix representing an arrangement of dots in a gray level of 50%; b) setting a dot at arbitrary one element on a highlight dot pattern which is a set of ON elements in said element matrix; c) repeating a process of adding a new dot to an element on said highlight dot pattern, said new dot being farthest from existing dots on said highlight dot pattern, on the premise of spatial repetition of said threshold matrix in halftoning of an original image, or repeating said process in accordance with a predetermined condition, to determine a turn-on order in which dots are added to elements in accordance with increase in gray level on a highlight side; d) setting dots at all elements excluding arbitrary one element on a shadow dot pattern which is a set of OFF elements in said element matrix; e) repeating a process of removing a dot of an element on said shadow dot pattern, said dot being farthest from elements in each of which a dot is not set on said shadow dot pattern, on the premise of spatial repetition of said threshold matrix, to determine a turn-off order in which dots are removed from elements in accordance with decrease in gray level on a shadow side; and f) determining a threshold value of each element in said matrix area in accordance with said turn-on order and said turn-off order.

Claim 24

21 . An electronic apparatus-readable recording medium in which data of a threshold matrix is recorded, said threshold matrix being compared with a grayscale original image in halftoning said original image, said data being generated by executing steps including the steps of: a) preparing a plurality of types of basic tiles each of which is an arrangement of elements in two rows and two columns consisting of two ON elements each representing existence of a dot and two OFF elements each representing absence of a dot, and arranging a plurality of basic tiles each of which is one of said plurality of types of basic tiles, in a matrix area where a threshold matrix is generated, in accordance with a prohibition condition for at least prohibiting an arrangement of only ON elements or OFF elements in an area of two rows and two columns, to acquire an element matrix representing an arrangement of dots in a gray level of 50%; b) setting a dot at arbitrary one element on a highlight dot pattern which is a set of ON elements in said element matrix; c) repeating a process of adding a new dot to an element on said highlight dot pattern, said new dot being farthest from existing dots on said highlight dot pattern, on the premise of spatial repetition of said threshold matrix in halftoning of an original image, or repeating said process in accordance with a predetermined condition, to determine a turn-on order in which dots are added to elements in accordance with increase in gray level on a highlight side; d) setting dots at all elements excluding arbitrary one element on a shadow dot pattern which is a set of OFF elements in said element matrix; e) repeating a process of removing a dot of an element on said shadow dot pattern, said dot being farthest from elements in each of which a dot is not set on said shadow dot pattern, on the premise of spatial repetition of said threshold matrix, to determine a turn-off order in which dots are removed from elements in accordance with decrease in gray level on a shadow side; and f) determining a threshold value of each element in said matrix area in accordance with said turn-on order and said turn-off order.

Claim 25

22 . The recording medium according to claim 21 , wherein said plurality of types of basic tiles are two types of arrangements in each of which said two ON elements are arranged diagonally.

Claim 26

23 . The recording medium according to claim 21 , wherein said two ON elements are arranged in a row direction or a column direction in each of said plurality of types of basic tiles.

Claim 27

24 . The recording medium according to claim 21 , wherein said step a) comprises the steps of: a1) setting a basic tile of one type at arbitrary one tile position in said matrix area; a2) setting a new basic tile of said one type at a tile position which is farthest from basic tiles of said one type in accordance with said prohibition condition, on the premise of spatial repetition of said threshold matrix; and a3) repeating said step a2) by a predetermined number of times.

Claim 28

25 . The recording medium according to claim 24 , wherein said step a) further comprises the steps of: a4) changing a type of a basic tile which is set at one tile position different from said arbitrary one tile position in said matrix area where said plurality of basic tiles are arranged, after said step a3); a5) changing a type of a basic tile which is set at a tile position farthest from basic tiles whose type has been changed, in accordance with said prohibition condition on the premise of spatial repetition of said threshold matrix; and a6) repeating said step a5) by a predetermined number of times.

Claim 29

26 . The recording medium according to claim 24 , wherein the number of elements in at least one of a row direction and a column direction in said element matrix is a value which is different from a power of two.

Claim 30

27 . The recording medium according to claim 21 , wherein said matrix area corresponds to one color component, and data of a threshold matrix of another color component which has a different size from a threshold matrix of said one color component is further recorded on said recording medium, said threshold matrix of said another color component being generated by performing said steps a) to f) in a matrix area of said another color component which is different from said matrix area of said one color component.

Claim 31

28 . The recording medium according to claim 21 , wherein resolutions in two directions which respectively corresponds to a row direction and a column direction in said matrix area, are different from each other in an image recording apparatus for recording a halftone image, which is generated by halftoning said original image, on an object, and a weighting coefficient for a distance in said row direction and a weighting coefficient for a distance in said column direction are different from each other in accordance with said resolutions in said two directions, when an element which is farthest from existing dots or an element which is farthest from elements where dots are not set is specified in each of said steps c) and e).

Claim 32

29 . The recording medium according to claim 21 , wherein a plurality of dots having different sizes can be formed on an object in an image recording apparatus for recording a halftone image, which is generated by halftoning said original image, on said object, and a step of generating a plurality of sub-threshold values used for determination of size of a dot from said threshold value of said each element in said matrix area, is further performed in generation of said data.

Claim 33

30 . The recording medium according to claim 21 , wherein a halftone image generated by halftoning said original image is recorded on an object by ejecting fine droplets of ink from a plurality of outlets arranged in a predetermined arrangement direction, in an image recording apparatus for recording said halftone image on said object, each element group which is a group of elements arranged in one direction out of a row direction and a column direction in said element matrix includes at least one ON element and the other direction corresponds to said arrangement direction of said plurality of outlets, and said predetermined condition in said step c) is that one of numbers 1 to α in said turn-on order is assigned to one element in said each element group in said element matrix where the number of elements in said other direction in said element matrix is α.