US5760920A
Expired / Lapsed
US
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System and method for generating calibrated dither matrices
Assignee: HP Inc
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Filing: 1994-09-19
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Granted: 1998-06-02
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Expires: 2014-09-19
Abstract
Abstract A method and a system for generating a dither matrix calibrated to a desired tonal response. The method and system comprise generating a dither matrix with a predicted tonal response, measuring the actual tonal response, manipulating a cumulative histogram for the dither matrix in response to the actual tonal response, and inputting the cumulative histogram to a dither matrix generation program to generate a dither matrix that conforms to the cumulative histogram. Other systems and methods are disclosed.
Inventors
- 👤 Qian Lin
- 👤 Brian Hoffmann
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 08:51
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/46; H04N1/52
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
73 words
A method of generating a dither matrix calibrated to a desired tonal response, comprising: (a) generating a dither matrix with a predicted tonal response close to the desired tonal response; (b) measuring actual tonal response; (c) manipulating a cumulative histogram for said dither matrix in response to said actual tonal response; and (d) inputting said cumulative histogram to a dither generation program to generate a dither matrix that conforms to said cumulative histogram.
Claim 2
Independent Claim
73 words
A method of generating a dither matrix calibrated to a desired tonal response, comprising: (a) generating a dither matrix with a predicted tonal response close to the desired tonal response; (b) measuring actual tonal response; (c) manipulating a cumulative histogram for said dither matrix in response to said actual tonal response; and (d) inputting said cumulative histogram to a dither generation program to generate a dither matrix that conforms to said cumulative histogram.
Claim 3
Dependent Claim
48 words
The method of claim 1 wherein step (c) comprises: (c.1) computing a difference between said tonal response and said desired tonal response; (c.2) using said difference to compute a modified cumulative histogram; and repeating steps (b) through (d) until said measured tonal response matches said desired tonal response.
Claim 4
Dependent Claim
30 words
The method of claim 2, wherein said step (a) comprises: using a model-based approach to compute a dither matrix having a tonal response approximating that of said desired tonal response.
Claim 5
Dependent Claim
14 words
The method of claim 3, wherein said model-based approach is a printer dot model.
Claim 6
Dependent Claim
66 words
The method of claim 1, wherein in step (b) tonal response is measured using at least one technique selected from the group consisting of a densitometer, digital output from a scanner, luminance measured with a spectrometer, luminance measured with a calorimeter, color differences obtained from processing CIE color specification measured using a spectrometer, and color differences obtained from processing CIE color specification measured using a colorimeter.
Claim 7
Dependent Claim
50 words
The method of claim 1, wherein step (c) comprises: (c.1) if the tonal response indicates that the output using the dither matrix is too dark, lowering the cumulative histogram; and (c.2) if the tonal response indicates that the output using the dither matrix is too light, raising the cumulative histogram.
Claim 8
Dependent Claim
93 words
The method of claim 1, wherein said calibrated dither matrix conforms to a desired tonal response function, f d (x) where x is a tone level, and wherein said dither matrix generated in step (a) has N×M threshold elements t ij , wherein said dither matrix has a tonal response function f o (x) where x is a tone level, and wherein step (d) comprises: (d.1) for each threshold value a, for each t ij that has the value a, setting t ij to equal a value that is a function of a.
Claim 9
Dependent Claim
17 words
The method of claim 7, wherein said function of a is f d -1 f o (a)!.
Claim 10
Dependent Claim
33 words
The method of claim 7 wherein f d (x) is linear and for each value a, for each t ij that has the value a, said function of a is f o (a).
Claim 11
Dependent Claim
36 words
The method of claim 7 wherein said actual tonal response has a range and further comprising: defining a range for the function f d to be a subset of said range of said actual tonal response.
Claim 12
Dependent Claim
26 words
The method of claim 1 wherein step (c) further comprises: (c.3) smoothing out discrete steps so that said cumulative histogram is a strictly monotonic cumulative histogram.
Claim 13
Independent Claim
209 words
A method for operating a computerized device, said computerized device having a processor, a memory, means for measuring a tonal response function, means for inputting an image into said memory, and means for manipulating the contents of said memory, to generate a calibrated dither matrix such that said calibrated dither matrix conforms to a desired tonal response function, f d (x) where x is a tone level, comprising: (a) in said processor, generating an initial dither matrix having N×M threshold elements t ij and storing said initial dither matrix in said memory; (b) measuring a tonal response function f o (x) from said initial dither matrix, where x is a tone level; and (c) in said processor, for each threshold value a, for each t ij that has the value a, setting t ij to equal f d -1 thereby generating a second dither matrix and storing said second dither matrix in said memory; (d) in said processor, calculating the cumulative histogram of the second dither matrix; (e) in said processor, smoothing out discrete steps in said cumulative histogram to generate a strictly monotonic cumulative histogram; and (f) inputting said monotonic cumulative histogram to a dither matrix generation program executable on said processor to generate a calibrated dither matrix.
Claim 14
Independent Claim
209 words
A method for operating a computerized device, said computerized device having a processor, a memory, means for measuring a tonal response function, means for inputting an image into said memory, and means for manipulating the contents of said memory, to generate a calibrated dither matrix such that said calibrated dither matrix conforms to a desired tonal response function, f d (x) where x is a tone level, comprising: (a) in said processor, generating an initial dither matrix having N×M threshold elements t ij and storing said initial dither matrix in said memory; (b) measuring a tonal response function f o (x) from said initial dither matrix, where x is a tone level; and (c) in said processor, for each threshold value a, for each t ij that has the value a, setting t ij to equal f d -1 thereby generating a second dither matrix and storing said second dither matrix in said memory; (d) in said processor, calculating the cumulative histogram of the second dither matrix; (e) in said processor, smoothing out discrete steps in said cumulative histogram to generate a strictly monotonic cumulative histogram; and (f) inputting said monotonic cumulative histogram to a dither matrix generation program executable on said processor to generate a calibrated dither matrix.
Claim 15
Dependent Claim
36 words
The method of claim 12 wherein said actual tonal response has a range and further comprising: defining a range for the function f d to be a subset of said range of said actual tonal response.
Claim 16
Dependent Claim
12 words
The method of claim 13 wherein the function f d is linear.
Claim 17
Independent Claim
153 words
A system for generating calibrated dither matrices used in halftone printing, comprising: (a) a central processing unit operable to execute computer programs; (b) a memory connected to said central processing unit; (c) a dither matrix generation program loaded into said memory, operable to accept a cumulative histogram as input and operable to create a dither matrix conforming to said cumulative histogram; (d) a halftone output device connected to said central processing unit; (e) a tonal response measuring device connected to said central processing unit; and (f) a control program loaded into said memory and operable to: 1. directing said dither matrix generation program to create an initial dither matrix; 2. directing said halftone output device to output sample outputs for each continuous tone level; 3. directing said tonal response measuring device to measure tonal response for each sample output; 4. compiling said tonal response for each sample output to a tonal response function;
Claim 18
Independent Claim
153 words
A system for generating calibrated dither matrices used in halftone printing, comprising: (a) a central processing unit operable to execute computer programs; (b) a memory connected to said central processing unit; (c) a dither matrix generation program loaded into said memory, operable to accept a cumulative histogram as input and operable to create a dither matrix conforming to said cumulative histogram; (d) a halftone output device connected to said central processing unit; (e) a tonal response measuring device connected to said central processing unit; and (f) a control program loaded into said memory and operable to: 1. directing said dither matrix generation program to create an initial dither matrix; 2. directing said halftone output device to output sample outputs for each continuous tone level; 3. directing said tonal response measuring device to measure tonal response for each sample output; 4. compiling said tonal response for each sample output to a tonal response function;
Claim 19
Dependent Claim
36 words
comparing said tonal response function to a desired tonal response function and generating a modified cumulative histogram; 6. directing said dither matrix generation program to use said modified cumulative histogram to generate a calibrated dither matrix.
Claim 20
Dependent Claim
36 words
comparing said tonal response function to a desired tonal response function and generating a modified cumulative histogram; 6. directing said dither matrix generation program to use said modified cumulative histogram to generate a calibrated dither matrix.
Claim 21
Independent Claim
208 words
A method for operating a computerized device, said computerized device having a processor, a memory, means for inputting an image into said memory, and means for manipulating the contents of said memory, to generate a calibrated dither matrix such that said calibrated dither matrix conforms to a desired tonal response function, f d (x) where x is a tone level and f d (x) is linear, comprising: (a) in said processor, generating an initial dither matrix having N×M threshold elements t ij and storing said initial dither matrix in said memory; (b) measuring a tonal response function f o (x) from said initial dither matrix, where x is a tone level; (c) in said processor, for each threshold value a, for each t ij that has the value a, setting t ij to equal f d -1 , thereby generating a second dither matrix and storing said second dither matrix in said memory; (d) in said processor, calculating the cumulative histogram of the second dither matrix; (e) in said processor, smoothing out discrete steps in said cumulative histogram to generate a strictly monotonic cumulative histogram; and (f) inputting said monotonic cumulative histogram to a dither matrix generation program executable on said processor to generate a calibrated dither matrix.
Claim 22
Independent Claim
208 words
A method for operating a computerized device, said computerized device having a processor, a memory, means for inputting an image into said memory, and means for manipulating the contents of said memory, to generate a calibrated dither matrix such that said calibrated dither matrix conforms to a desired tonal response function, f d (x) where x is a tone level and f d (x) is linear, comprising: (a) in said processor, generating an initial dither matrix having N×M threshold elements t ij and storing said initial dither matrix in said memory; (b) measuring a tonal response function f o (x) from said initial dither matrix, where x is a tone level; (c) in said processor, for each threshold value a, for each t ij that has the value a, setting t ij to equal f d -1 , thereby generating a second dither matrix and storing said second dither matrix in said memory; (d) in said processor, calculating the cumulative histogram of the second dither matrix; (e) in said processor, smoothing out discrete steps in said cumulative histogram to generate a strictly monotonic cumulative histogram; and (f) inputting said monotonic cumulative histogram to a dither matrix generation program executable on said processor to generate a calibrated dither matrix.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2001-06-01 | 2001-12-01 | 2002-06-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-06-01 | 2005-12-01 | 2006-06-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-06-01 | 2009-12-01 | 2010-06-02 | $7700.00 | Window Closed / Lapsed |