Patent US4800443A successfully refreshed from Google Patents.
US4800443A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and apparatus for carrying out a dithering operation
Assignee: Tektronix Inc
•
Filing: 1987-08-14
•
Granted: 1989-01-24
•
Expires: 2007-08-14
Abstract
Abstract A two-dimensional array of binary values is used to control operation of a bi-level imaging device. The array of binary values is formed by applying an enhanced array g(u,v) to a two-dimensional array of threshold values. A two-dimensional array of pixel value f(u,v) is used to form the enhanced array g(u,v) such that g(u,v)=m f +k[f(u,v)-m f ] where m f is the average value of f(u+a, v+b) from a=-L to a=+L and b=-M to b=+M and k is a gain function which depends on the standard deviation in f(u+c, v+d) from c=-N to c=+N and d=-P to d=+P. L, M, N and P define the sub-array over which the standard deviation is calculated. Preferably, L, M, N and P are each equal to 2. The value of k is a decreasing function of the standard deviation: the larger the standard deviation, the smaller the gain factor k. The rate at which k decreases with increase in the standard deviation depends on the edge sampling characteristics of the array of threshold values.
Inventors
- 👤 Regis J. Crinon
- 👤 Yih-Chyun Jenq
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 05:13
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/405; H04N1/4051
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
158 words
A method of controlling operation of an imaging device in response to a two-dimensional array of pixel values f(u,v) representing an image having an edge of amplitude C, comprising: (a) forming an enhanced array of pixel values g(u,v) from the values f(u,v), (b) forming atwo-dimensional array of binary values h(u,v) by applying the enhanced array to a two-dimensional array of threshold values t(u,v), and (c) applying the two-dimensional array of binary values to the imaging device for controlling the operation thereof, wherein g(u,v)=m f +k[f(u,v)-m f ] where m f is the average value of f(u,v) over a predetermined number of pixels in the neighborhood of the pixel (u,v) and k is dependent on both the standard deviation in f(u,v) over a predetermined number of pixels in the neighborhood of the pixel (u,v) and a number which is inversely proportional to the distance between the point (u,v) and a point (x,y) such that t(x,y)-t(u,v) is less than C.
Claim 2
Independent Claim
158 words
A method of controlling operation of an imaging device in response to a two-dimensional array of pixel values f(u,v) representing an image having an edge of amplitude C, comprising: (a) forming an enhanced array of pixel values g(u,v) from the values f(u,v), (b) forming atwo-dimensional array of binary values h(u,v) by applying the enhanced array to a two-dimensional array of threshold values t(u,v), and (c) applying the two-dimensional array of binary values to the imaging device for controlling the operation thereof, wherein g(u,v)=m f +k[f(u,v)-m f ] where m f is the average value of f(u,v) over a predetermined number of pixels in the neighborhood of the pixel (u,v) and k is dependent on both the standard deviation in f(u,v) over a predetermined number of pixels in the neighborhood of the pixel (u,v) and a number which is inversely proportional to the distance between the point (u,v) and a point (x,y) such that t(x,y)-t(u,v) is less than C.
Claim 3
Dependent Claim
21 words
A method according to claim 1, wherein the standard deviation is approximated by the absolute moment of the value of f(u,v).
Claim 4
Dependent Claim
44 words
A method according to claim 1, wherein the two-dimensional array of threshold values samples edges of amplitude Ci at spatial frequencies f Ci and the value of k is larger for small values of f Ci than for larger values of f Ci .
Claim 5
Dependent Claim
25 words
A method according to claim 1, wherein the two-dimensional array of threshold values is composed of a plurality of identical two-dimensional sub-arrays in non-overlapping relationship.
Claim 6
Dependent Claim
14 words
A method according to claim 4, wherein the two-dimensional sub-array is a square array.
Claim 7
Dependent Claim
14 words
A method according to claim 5, wherein the square array is a magic square.
Claim 8
Dependent Claim
136 words
Apparatus for processing a two-dimensional array of pixel values f(u,v) representing an image having an edge of amplitude C, comprising: means for forming an enhanced array of pixel values g(u,v) from the values f(u,v), and means for forming a two-dimensional array of binary values h(u,v) by applying the enhanced array g(u,v) to a two-dimensional array of threshold values t(u,v) wherein g(u,v)=m f +k[f(u,v)-m f ] where m f is the average value of f(u,v) over a predetermined number of pixels in the neighborhood of the pixel (u,v) and k is dependent on both the standard deviation in f(u,v) over a predetermined number of pixels in the neighborhood of the pixel (u,v) and a number which is inversely proportional to the distance between the point (u,v) and a point (x,y) such that t(x,y)-t(u,v) is less than C.
Claim 9
Dependent Claim
136 words
Apparatus for processing a two-dimensional array of pixel values f(u,v) representing an image having an edge of amplitude C, comprising: means for forming an enhanced array of pixel values g(u,v) from the values f(u,v), and means for forming a two-dimensional array of binary values h(u,v) by applying the enhanced array g(u,v) to a two-dimensional array of threshold values t(u,v) wherein g(u,v)=m f +k[f(u,v)-m f ] where m f is the average value of f(u,v) over a predetermined number of pixels in the neighborhood of the pixel (u,v) and k is dependent on both the standard deviation in f(u,v) over a predetermined number of pixels in the neighborhood of the pixel (u,v) and a number which is inversely proportional to the distance between the point (u,v) and a point (x,y) such that t(x,y)-t(u,v) is less than C.
Claim 10
Dependent Claim
30 words
Apparatus according to claim 7, further comprising a bi-level imaging device and means for applying the array of binary values to the bi-level imaging device to control the operation thereof.
References Cited (Backward Citations)
US4710822A
Cited
US4741046A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-01-24 | 1992-07-25 | 1993-01-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-01-24 | 1996-07-25 | 1997-01-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-01-24 | 2000-07-25 | 2001-01-24 | $7700.00 | Window Closed / Lapsed |