EP0304289A2
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Half-tone image reproduction method and apparatus
Assignee: Toshiba Corp
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Filing: 1988-08-17
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Granted: —
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Expires: 2008-08-17
Abstract
Abstract A half-tone image reproduction apparatus, which comprises a Dither matrix memory (12), constituted by a plurality of elements, for storing a multi-level Dither matrix having multi threshold levels assigned to the individual elements, input data supplying means (10, 11) for supplying the element on the Dither matrix (12) and an input density level, and print dot forming means (13, 14) for forming print dots in accordance with the energy control level selectively read out from the Dither matrix memory (12). The energy control level stored in the Dither matrix memory (12) is set in accordance with rules for changing the energy control level in accordance with a change in input density level. These rules are independently suitably determined for the respective partial density ranges which constitute a whole density range for the input density. According to this invention, gradation jump and deformation at a high density region can be prevented so that a half-tone image with smooth gradation and high resolution can be attained.
Inventors
- 👤 Shuzo C/O Patent Division Hirahara
- 👤 Kiyoshi C/O Patent Division Yamada
- 👤 Kazuhiko C/O Patent Division Higuchi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 23:14
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/40087
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
185 words
A half-tone image reproduction method comprising the steps of storing a Dither matrix consisting of M (M being an integer greater than or equal to 2) elements for expressing a pseudo half-tone image as a whole, each element of said Dither matrix having an information representing the relation between an input density level and an energy control level, said energy control level for each element being determined by N (N being an integer greater than or equal to 2) different threshold levels with respect to the input density level, for selecting the energy control level by specifying the element on said Dither matrix and the input density level, and for forming a print dot in accordance with said energy control level, characterized in that a whole density range for the input density level is divided into a plurality of partial density range, said energy control level for each element is set in accordance with different rules, each rule providing an independent and suitable change in energy control level with a change in input density level for each of a plurality of the partial density ranges.
Claim 2
Dependent Claim
185 words
A half-tone image reproduction method comprising the steps of storing a Dither matrix consisting of M (M being an integer greater than or equal to 2) elements for expressing a pseudo half-tone image as a whole, each element of said Dither matrix having an information representing the relation between an input density level and an energy control level, said energy control level for each element being determined by N (N being an integer greater than or equal to 2) different threshold levels with respect to the input density level, for selecting the energy control level by specifying the element on said Dither matrix and the input density level, and for forming a print dot in accordance with said energy control level, characterized in that a whole density range for the input density level is divided into a plurality of partial density range, said energy control level for each element is set in accordance with different rules, each rule providing an independent and suitable change in energy control level with a change in input density level for each of a plurality of the partial density ranges.
Claim 3
Dependent Claim
115 words
The half-tone image reproduction method according to claim 1, characterized in that said energy control level for each element is determined by first rule in a low density range for changing an energy control level of a specific element while giving a constant low energy control level to elements around said specific element, second rule in an intermediate range for generally changing energy control levels of a plurality of elements by a substantially same amount, and third rule in a high density range for changing an energy control level of only a specific element and changing energy control levels of other elements when said energy control level of said specific element reaches a predetermined level.
Claim 4
Dependent Claim
66 words
The half-tone image reproduction method according to claim 1, characterized in that said Dither matrix for use in one of the partial density range is constituted by fixed elements fixed to a constant energy control level p and one variable element whose energy control level is changed to a level greater than said constant energy control level p in accordance with a density to be reproduced.
Claim 5
Dependent Claim
70 words
The half-tone image reproduction method according to claim 1, characterized in that said Dither matrix for use in one of the partial range is constituted by a group of fixed elements fixed to at least two energy control levels p and P (0 < p < P ≦ N) and one variable element whose energy control level is changed between 0 and P in accordance with an input density level.
Claim 6
Dependent Claim
51 words
The half-tone image reproduction method according to claim 1, characterized in that said Dither matrix for use in one of the partial density range is constituted by a group of Q (2 ≦ Q < M) variable elements whose energy control levels are changed in accordance with an input density level.
Claim 7
Dependent Claim
45 words
The half-tone image reproduction method according to claim 5, characterized in that said Dither matrix includes at least one element of a constant energy control level R (0 < R ≦ N) in a group of fixed elements other than said group of variable elements.
Claim 8
Dependent Claim
51 words
The half-tone image reproduction method according to claim 1, characterized in that said Dither matrix for use in one of the partial density range includes both of an element whose energy control level is increased and an element whose energy control level is decreased with a change in input density level.
Claim 9
Dependent Claim
217 words
A half-tone image reproduction apparatus comprising: a Dither matrix memory (12) for storing a Dither matrix consisting of M (M being an integer greater than or equal to 2) elements for expressing a pseudo half-tone image as a whole, each element of said Dither matrix having an information representing the relation between an input density level and an energy control level, said energy control level for each element being determined by N (N being an integer greater than or equal to 2) different threshold levels with respect to the input density level, input data supplying means (10, 11) for supplying to said Dither matrix memory (12) the element on said Dither matrix and the input density level as input data, and print dot forming means (13, 14) for forming a print dot in accordance with energy control level data selectively read out from said Dither matrix memory (12), characterized in that a whole density range for the input density level is divided into a plurality of partial density range, said Dither matrix memory (12) stores energy control level for each element being set in accordance with different rules, each rule providing an independent and suitable change in energy control level with a change in input density level for each of a plurality of the partial density ranges.
Claim 10
Dependent Claim
217 words
A half-tone image reproduction apparatus comprising: a Dither matrix memory (12) for storing a Dither matrix consisting of M (M being an integer greater than or equal to 2) elements for expressing a pseudo half-tone image as a whole, each element of said Dither matrix having an information representing the relation between an input density level and an energy control level, said energy control level for each element being determined by N (N being an integer greater than or equal to 2) different threshold levels with respect to the input density level, input data supplying means (10, 11) for supplying to said Dither matrix memory (12) the element on said Dither matrix and the input density level as input data, and print dot forming means (13, 14) for forming a print dot in accordance with energy control level data selectively read out from said Dither matrix memory (12), characterized in that a whole density range for the input density level is divided into a plurality of partial density range, said Dither matrix memory (12) stores energy control level for each element being set in accordance with different rules, each rule providing an independent and suitable change in energy control level with a change in input density level for each of a plurality of the partial density ranges.
Claim 11
Dependent Claim
119 words
The half-tone image reproduction apparatus according to claim 8, characterized in that said Dither matrix memory stores said energy control level for each element determined by first rule in a low density range for changing an energy control level of a specific element while giving a constant low energy control level to elements around said specific element, second rule in an intermediate range for generally changing energy control levels of a plurality of elements by a substantially same amount, and third rule in a high density range for changing an energy control level of only a specific element and changing energy control levels of other elements when said energy control level of said specific element reaches a predetermined level.
Claim 12
Dependent Claim
72 words
The half-tone image reproduction apparatus according to claim 8, characterized in that said Dither matrix memory stores said Dither matrix for use in one of the partial density range which is constituted by fixed elements fixed to a constant energy control level p and one variable element whose energy control level is changed to a level greater than said constant energy control level p in accordance with a density to be reproduced.
Claim 13
Dependent Claim
76 words
The half-tone image reproduction apparatus according to claim 8, characterized in that said Dither matrix memory stores said Dither matrix for use in one of the partial range which is constituted by a group of fixed elements fixed to at least two energy control levels p and P (0 < p < P ≦ N) and one variable element whose energy control level is changed between 0 and P in accordance with an input density level.
Claim 14
Dependent Claim
56 words
The half-tone image reproduction apparatus according to claim 8, characterized in that said Dither matrix memory stores said Dither matrix for use in one of the partial density range is constituted by a group of Q (2 ≦ Q < M) variable elements whose energy control levels are changed in accordance with an input density level.
Claim 15
Dependent Claim
50 words
The half-tone image reproduction apparatus according to claim 12, characterized in that said Dither matrix memory stores said Dither matrix including at least one element of a constant energy control level R (0 < R ≦ N) in a group of fixed elements other than said group of variable elements.
Claim 16
Dependent Claim
56 words
The half-tone image reproduction apparatus according to claim 8, characterized in that said Dither matrix memory stores said Dither matrix for use in one of the partial density range including both of an element whose energy control level is increased and an element whose energy control level is decreased with a change in input density level.
Claim 17
Dependent Claim
225 words
A half-tone image reproduction method comprising the steps of storing a Dither matrix consisting of M (M being an integer greater than or equal to 2) elements for expressing a pseudo half-tone image as a whole, each element of said Dither matrix having an information representing the relation between an input density level and an energy control level, said energy control level for each element being determined by N (N being an integer greater than or equal to 2) different threshold levels with respect to the input density level, for selecting the energy control level by specifying the element on said Dither matrix and the input density level, and for forming a print dot in accordance with said energy control level, characterized in that a whole density range for the input density level is divided into a plurality of partial density range, said energy control level for each element is set in accordance with different rules, the rule for use in at least one of the partial range providing a change in energy control level with a change in input density level, said change in energy control level being set in such a way that a dot pattern expands or contracts along a line extending in a main scanning direction and a subscanning direction passing a position -f a fixed element in said Dither matrix.
Claim 18
Dependent Claim
225 words
A half-tone image reproduction method comprising the steps of storing a Dither matrix consisting of M (M being an integer greater than or equal to 2) elements for expressing a pseudo half-tone image as a whole, each element of said Dither matrix having an information representing the relation between an input density level and an energy control level, said energy control level for each element being determined by N (N being an integer greater than or equal to 2) different threshold levels with respect to the input density level, for selecting the energy control level by specifying the element on said Dither matrix and the input density level, and for forming a print dot in accordance with said energy control level, characterized in that a whole density range for the input density level is divided into a plurality of partial density range, said energy control level for each element is set in accordance with different rules, the rule for use in at least one of the partial range providing a change in energy control level with a change in input density level, said change in energy control level being set in such a way that a dot pattern expands or contracts along a line extending in a main scanning direction and a subscanning direction passing a position -f a fixed element in said Dither matrix.
Claim 19
Dependent Claim
37 words
The half-tone image reproduction method according to claim 15, characterized in that said Dither matrix for use in one of the partial density range is determined in such a way as to form a cross-shaped dot pattern.
Claim 20
Dependent Claim
37 words
The half-tone image reproduction method according to claim 15, characterized in that said Dither matrix for use in one of the partial density range is determined in such a way as to form a cross-shaped blank pattern.
Claim 21
Dependent Claim
54 words
The half-tone image reproduction method according to claim 15, characterized in that said Dither matrix for use in one of the partial density range is determined in such a way that said dot pattern is coupled at one point to at least one of four dot patterns surrounding and adjacent to said dot pattern.
Claim 22
Dependent Claim
40 words
The half-tone image reproduction method according to claim 15, characterized in that said Dither matrix is determined in such a way that the fixed element is an element at a center, or a center of gravity, of said Dither matrix.
Claim 23
Dependent Claim
47 words
The half-tone image reproduction method according to claim 15, characterized in that said Dither matrix for use in one of the partial density range is determined in such a way that said dot pattern is an isolated pattern not abutting on a periphery of said Dither matrix.
Claim 24
Dependent Claim
257 words
A half-tone image reproduction apparatus comprising: a Dither matrix memory (12) for storing a Dither matrix consisting of M (M being an integer greater than or equal to 2) elements for expressing a pseudo half-image as a whole, each element of said Dither matrix having an information representing the relation between an input density level and an energy control level, said energy control level for each element being determined by N (N being an integer greater than or equal to 2) different threshold levels with respect to the input density level, input data supplying means (10, 11) for supplying to said Dither matrix memory (12) the element on said Dither matrix and the input density level as input data, and print dot forming means (13, 14) for forming a print dot in accordance with energy control level data selectively read out from said Dither matrix memory (12), characterized in that a whole density range for the input density level is divided into a plurality of partial density range, said Dither matrix memory (12) stores said energy control level for each element being set in accordance with different rules, the rule for use in at least one of the partial range providing a change in energy control level with a change in input density level, said change in energy control level being set in such a way that a dot pattern expands or contracts along a line extending in a main scanning direction and a subscanning direction passing a position of a specific element in said Dither matrix.
Claim 25
Dependent Claim
257 words
A half-tone image reproduction apparatus comprising: a Dither matrix memory (12) for storing a Dither matrix consisting of M (M being an integer greater than or equal to 2) elements for expressing a pseudo half-image as a whole, each element of said Dither matrix having an information representing the relation between an input density level and an energy control level, said energy control level for each element being determined by N (N being an integer greater than or equal to 2) different threshold levels with respect to the input density level, input data supplying means (10, 11) for supplying to said Dither matrix memory (12) the element on said Dither matrix and the input density level as input data, and print dot forming means (13, 14) for forming a print dot in accordance with energy control level data selectively read out from said Dither matrix memory (12), characterized in that a whole density range for the input density level is divided into a plurality of partial density range, said Dither matrix memory (12) stores said energy control level for each element being set in accordance with different rules, the rule for use in at least one of the partial range providing a change in energy control level with a change in input density level, said change in energy control level being set in such a way that a dot pattern expands or contracts along a line extending in a main scanning direction and a subscanning direction passing a position of a specific element in said Dither matrix.
Claim 26
Dependent Claim
42 words
The half-tone image reproduction apparatus according to claim 21, characterized in that said Dither matrix memory stores said energy control level for each element determined in such a way as to form a cross-shaped dot pattern in one of the partial density.
Claim 27
Dependent Claim
43 words
The half-tone image reproduction apparatus according to claim 21, characterized in that said Dither matrix memory stores said energy control level for each element determined in such a way as to form a cross-shaped blank pattern in one of the partial density range.
Claim 28
Dependent Claim
60 words
The half-tone image reproduction apparatus according to claim 21, characterized in that said Dither matrix memory stores said energy control level for each element determined in such a way that said dot pattern is coupled at one point to at least one of four dot patterns surrounding and adjacent to said dot pattern in one of the partial density range.
Claim 29
Dependent Claim
48 words
The half-tone image reproduction apparatus according to claim 21, characterized in that said Dither matrix memory stores said energy control level for each element determined in such a way that the fixed element is an element at a center, or a center of gravity, of said Dither matrix.
Claim 30
Dependent Claim
53 words
The half-tone image reproduction apparatus according to claim 21, characterized in that said Dither matrix memory stores said energy control level for each element determined in such a way that said dot pattern is an isolated pattern not abutting on a periphery of said Dither matrix in one of the partial density range.
References Cited (Backward Citations)
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