Halftoning with uniformly dispersed dot growth
First Claim
1. A method for reproducing a contone image as a halftone image on a recording medium, using threshold values in a threshold matrix, comprising the steps of:
- (a) providing a base supercell suitable for periodically tiling a plane, the base supercell having a plurality of microdots and a plurality of virtual halftone dot centers;
(b) assigning an ordering sequence comprising a series of numbers on the virtual halftone dot centers in the base supercell by;
(i) assigning a first number in the ordering sequence to a first virtual halftone dot center in the base supercell;
(ii) assigning a second consecutive number in the ordering sequence to a second virtual halftone dot center in the base supercell;
(iii) calculating a value of an aggregate distance function for each virtual halftone dot center in the base supercell not already included in the ordering sequence;
(iv) selecting a next virtual halftone dot center in the base supercell in response to the calculated aggregate distance function, the next virtual halftone dot center having one of the least values of the calculated aggregate distance function;
(v) assigning the next consecutive number in the ordering sequence to the selected next virtual halftone dot center in the base supercell; and
(vi) repeating steps (iii), (iv), and (v), until each virtual halftone dot center in the base supercell is included in the ordering sequence;
(c) assigning threshold values to microdots in response to the ordering sequence thereby generating the threshold matrix in the base supercell; and
(d) using the threshold matrix in combination with the contone image to generate a screened halftone image on the recording medium.
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Accused Products
Abstract
In general, in one aspect, the invention features a method for reproducing a contone image as a halftone image on a recording medium, using threshold values in a threshold matrix, including the steps of providing a base supercell suitable for periodically tiling a plane, which has a plurality of microdots and a plurality of virtual halftone dot centers; assigning an ordering sequence consisting of a series of numbers on the virtual halftone dot centers in the base supercell; assigning threshold values to microdots in response to the ordering sequence thereby generating the threshold matrix in the base supercell; and using the threshold matrix in combination with the contone image to generate a screened halftone image on the recording medium. The step of assigning an ordering sequence includes: (i) assigning a first number in the ordering sequence to a first virtual halftone dot center in the base supercell; (ii) assigning a second consecutive number in the ordering sequence to a second virtual halftone dot center in the base supercell; (iii) calculating a value of an aggregate distance function for each virtual halftone dot center in the base supercell not already included in the ordering sequence; (iv) selecting a next virtual halftone dot center in the base supercell in response to the calculated aggregate distance function, the next virtual halftone dot center having one of the least values of the calculated aggregate distance function; (v) assigning the next consecutive number in the ordering sequence to the selected next virtual halftone dot center in the base supercell; and then repeating steps (iii), (iv), and (v), until each virtual halftone dot center in the base supercell is included in the ordering sequence.
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Citations
44 Claims
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1. A method for reproducing a contone image as a halftone image on a recording medium, using threshold values in a threshold matrix, comprising the steps of:
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(a) providing a base supercell suitable for periodically tiling a plane, the base supercell having a plurality of microdots and a plurality of virtual halftone dot centers;
(b) assigning an ordering sequence comprising a series of numbers on the virtual halftone dot centers in the base supercell by;
(i) assigning a first number in the ordering sequence to a first virtual halftone dot center in the base supercell;
(ii) assigning a second consecutive number in the ordering sequence to a second virtual halftone dot center in the base supercell;
(iii) calculating a value of an aggregate distance function for each virtual halftone dot center in the base supercell not already included in the ordering sequence;
(iv) selecting a next virtual halftone dot center in the base supercell in response to the calculated aggregate distance function, the next virtual halftone dot center having one of the least values of the calculated aggregate distance function;
(v) assigning the next consecutive number in the ordering sequence to the selected next virtual halftone dot center in the base supercell; and
(vi) repeating steps (iii), (iv), and (v), until each virtual halftone dot center in the base supercell is included in the ordering sequence;
(c) assigning threshold values to microdots in response to the ordering sequence thereby generating the threshold matrix in the base supercell; and
(d) using the threshold matrix in combination with the contone image to generate a screened halftone image on the recording medium. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A screen, suitable for the transformation of a contone image into a halftone image, said screen comprising a plurality of discrete spotlike zones arranged on grid points of a periodic grid defined by a screen angle and a screen ruling, wherein the spotlike zones are generated by using threshold values in a threshold matrix, the threshold matrix produced by:
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(a) providing a base supercell suitable for periodically tiling a plane, the base supercell having a plurality of microdots and a plurality of virtual halftone dot centers;
(b) assigning an ordering sequence comprising a series of numbers on the virtual halftone dot centers in the base supercell by;
(i) assigning a first number in the ordering sequence to a first virtual halftone dot center in the base supercell;
(ii) assigning a second consecutive number in the ordering sequence to a second virtual halftone dot center in the base supercell;
(iii) calculating a value of an aggregate distance function for each virtual halftone dot center in the base supercell not already included in the ordering sequence;
(iv) selecting a next virtual halftone dot center in the base supercell in response to the calculated aggregate distance function, the next virtual halftone dot center having one of the least values of the calculated aggregate distance function;
(v) assigning the next consecutive number in the ordering sequence to the selected next virtual halftone dot center in the base supercell; and
(vi) repeating steps (iii), (iv), and (v), until each virtual halftone dot center in the base supercell is included in the ordering sequence;
(c) assigning threshold values to microdots in response to the ordering sequence thereby generating the threshold matrix in the base supercell. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A screening system for converting contone image information to a halftone image information, the screening system comprising means for generating, retrieving or storing a screen suited for the transformation of a continuous tone image into a halftone image, wherein said screen comprises a plurality of discrete spotlike zones generated by using threshold values in a threshold matrix, the threshold matrix produced by:
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(a) providing a base supercell suitable for periodically tiling a plane, the base supercell having a plurality of microdots and a plurality of virtual halftone dot centers arranged on a periodic grid having a screen angle and screen ruling;
(b) assigning an ordering sequence comprising a series of numbers on the virtual halftone dot centers in the base supercell by;
(i) assigning a first number in the ordering sequence to a first virtual halftone dot center in the base supercell;
(ii) assigning a second consecutive number in the ordering sequence to a second virtual halftone dot center in the base supercell;
(iii) calculating a value of an aggregate distance function for each virtual halftone dot center in the base supercell not already included in the ordering sequence;
(iv) selecting a next virtual halftone dot center in the base supercell in response to the calculated aggregate distance function, the next virtual halftone dot center having one of the least values of the calculated aggregate distance function;
(v) assigning the next consecutive number in the ordering sequence to the selected next virtual halftone dot center in the base supercell; and
(vi) repeating steps (iii), (iv), and (v), until each virtual halftone dot center in the base supercell is included in the ordering sequence;
(c) assigning threshold values to microdots in response to the ordering sequence thereby generating the threshold matrix in the base supercell. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27)
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28. A method for reproducing a contone image as a multi-color halftone image on a recording medium, using threshold values in threshold matrices, comprising the steps of:
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(a) providing a first base supercell suitable for periodically tiling a plane, the first base supercell having a first plurality of microdots and a first plurality of virtual halftone dot centers;
(b) providing a second base supercell suitable for periodically tiling a plane, the second base supercell having a second plurality of microdots and a second plurality of virtual halftone dot centers;
(c) assigning a first ordering sequence and a second ordering sequence to the virtual halftone dot centers in both base supercells, each ordering sequence comprising series of numbers, by;
(i) assigning a first number in the first ordering sequence to a first virtual halftone dot center in the first base supercell;
(ii) assigning a first number in the second ordering sequence to a first virtual halftone dot center in the second base supercell;
(iii) calculating a value of a combined aggregate distance function for each virtual halftone dot center from a first plurality of virtual halftone dot centers in the first base supercell not already included in the first ordering sequence;
(iv) selecting a first next virtual halftone dot center in the first base supercell in response to the value of the combined aggregate distance function calculated in step (iii), the first next virtual halftone dot center having one of the least values of the combined calculated aggregate distance function;
(v) assigning the next consecutive number in the first ordering sequence to the selected first next virtual halftone dot center in the first base supercell;
(vi) calculating a value of an combined aggregate distance function for each virtual halftone dot center from a second plurality of virtual halftone dot centers in the second base supercell not already included in the second ordering sequence;
(vii) selecting a second next virtual halftone dot center in the second base supercell in response to the value of the combined aggregate distance function calculated in step (vi), the second next virtual halftone dot center having one of the least values of the combined calculated aggregate distance function;
(viii) assigning the next consecutive number in the second ordering sequence to the selected second next virtual halftone dot center in the second base supercell;
(ix) repeating steps (iii) through (viii), until each virtual halftone dot center in the first base supercell is included in the first ordering sequence and each virtual halftone dot center in the second base supercell is included in the second ordering sequence;
(d) assigning threshold values to microdots in response to the first ordering sequence thereby generating the first threshold matrix in the first base supercell;
(e) assigning threshold values to microdots in response to the second ordering sequence thereby generating the second threshold matrix in the second base supercell; and
(f) using the first threshold matrix and the second threshold matrix in combination with the contone image to generate a screened multi-color halftone image on the recording medium. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44)
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Specification