US6608702B1
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Method for generating threshold patterns and gradation image binarizing device
Assignee: Oki Electric Industry Co Ltd
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Filing: 1999-07-12
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Granted: 2003-08-19
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Expires: 2019-07-12
Abstract
Abstract There is disclosed a method wherein an origin is set on the dither pattern and the dither pattern is rotated relative to the origin by a required screen angle. By rotating the dither pattern, real-number coordinates of an origin of adjacent dither patterns are obtained. Coordinates of the origin of the adjacent dither pattern are corrected by rounding fractions of the real-coordinate so that the real-number coordinates are changed to integer coordinates. An angle which a segment connecting an origin of the dither pattern to be based on and that of the adjacent dither pattern obtained after the correction forms with a horizontal line is selected as a screen angle. By this, the shape of the dither pattern obtained after being rotated becomes uniform, preventing the occurrence of moire.
Inventors
- 👤 Koji Urasawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 16:54
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/405; H04N1/4055; H04N1/4058
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
152 words
A method for converting a gradation image, having picture elements with values which are represented by multivalues, to a dot image having a selected screen angle, and for generating a threshold pattern wherein threshold values are assigned at a pitch of an array of dots in said dot image to binarize said picture elements, comprising steps of: setting an origin of said threshold pattern and obtaining real-number coordinates of an origin of an adjacent threshold pattern by rotating said threshold pattern relative to said set origin by a predetermined screen angle; correcting the coordinates of said origin of said adjacent threshold pattern so that said real-number coordinates are changed to integer coordinates by rounding fractions of said real-number coordinates; and selecting, as said selected screen angle, an angle which a segment connecting said set origin and the origin of said adjacent threshold pattern obtained after the correction forms with a horizontal line.
Claim 2
Independent Claim
152 words
A method for converting a gradation image, having picture elements with values which are represented by multivalues, to a dot image having a selected screen angle, and for generating a threshold pattern wherein threshold values are assigned at a pitch of an array of dots in said dot image to binarize said picture elements, comprising steps of: setting an origin of said threshold pattern and obtaining real-number coordinates of an origin of an adjacent threshold pattern by rotating said threshold pattern relative to said set origin by a predetermined screen angle; correcting the coordinates of said origin of said adjacent threshold pattern so that said real-number coordinates are changed to integer coordinates by rounding fractions of said real-number coordinates; and selecting, as said selected screen angle, an angle which a segment connecting said set origin and the origin of said adjacent threshold pattern obtained after the correction forms with a horizontal line.
Claim 3
Dependent Claim
63 words
The method for generating a threshold pattern according to claim 1 , further comprising the step of obtaining additional threshold patterns so that threshold patterns cover all of the dots of the dot image, wherein all of the threshold patterns have the same shape and wherein all values of each threshold pattern assigned at corresponding sites in each threshold pattern are the same.
Claim 4
Dependent Claim
81 words
The method for generating a threshold pattern according to claim 1 wherein coordinates (X, Y) of said threshold pattern existing before being rotated are related by an operational processing to coordinates (X′, Y′) of each threshold value of said threshold pattern obtained after being rotated, a threshold value assigned at coordinates (X,Y) of said threshold pattern existing before being rotated is selected, and the selected threshold value is used as a threshold value of said threshold pattern obtained after being rotated.
Claim 5
Dependent Claim
36 words
The method for generating a threshold pattern according to claim 3 wherein, in said operational processing, an affine transformation is performed using a magnification of a threshold pattern edge and a corrected screen angle as factors.
Claim 6
Dependent Claim
185 words
A gradation image binarizing device comprising: a threshold pattern storing section used to store a threshold pattern for binarization; a gradation image storing section used to store a gradation image to be binarized by said threshold pattern; a parameter storing section used to store a rotation parameter obtained from a screen angle after correction which is carried out in a manner such that an origin is set for said pattern and real-number coordinates of an origin of an adjacent threshold pattern are obtained by rotating said threshold pattern relative to said set origin by a predetermined screen angle and such that coordinates of said origin of said adjacent threshold pattern are corrected so that said real-number coordinates are changed to integer coordinates by rounding fractions of said real-number coordinates and an angle which a segment connecting said set origin and the origin of the adjacent dither pattern obtained after said correction forms with a horizontal line is selected as a screen angle; and a means, responsive to said threshold pattern and a rotation parameter stored in said parameter storing section, for binarizing said gradation image.
Claim 7
Dependent Claim
185 words
A gradation image binarizing device comprising: a threshold pattern storing section used to store a threshold pattern for binarization; a gradation image storing section used to store a gradation image to be binarized by said threshold pattern; a parameter storing section used to store a rotation parameter obtained from a screen angle after correction which is carried out in a manner such that an origin is set for said pattern and real-number coordinates of an origin of an adjacent threshold pattern are obtained by rotating said threshold pattern relative to said set origin by a predetermined screen angle and such that coordinates of said origin of said adjacent threshold pattern are corrected so that said real-number coordinates are changed to integer coordinates by rounding fractions of said real-number coordinates and an angle which a segment connecting said set origin and the origin of the adjacent dither pattern obtained after said correction forms with a horizontal line is selected as a screen angle; and a means, responsive to said threshold pattern and a rotation parameter stored in said parameter storing section, for binarizing said gradation image.
References Cited (Backward Citations)
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| 3.5 Years (Year 4) | 2006-08-18 | 2007-02-17 | 2007-08-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2010-08-18 | 2011-02-17 | 2011-08-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2014-08-18 | 2015-02-17 | 2015-08-19 | $7700.00 | Window Closed / Lapsed |