US5748336A
Expired / Lapsed
US
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Image processing method and image processing apparatus
Assignee: Seiko Epson Corp
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Filing: 1996-10-07
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Granted: 1998-05-05
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Expires: 2016-10-07
Abstract
Abstract An image processing method for converting multi-gradation image data into two-gradation image data by employing an error diffusion method, the image processing method comprises the steps of: (1) adding a diffusion error derived from at least one pixel which has already been binary-coded and is located near a pixel of interest to multi-gradation image data of this pixel of interest to thereby obtain corrected data; (2) comparing the corrected data with a threshold value and converting the corrected data into two-gradation image data for indicating any one of a dot ON and a dot OFF; (3) calculating a quantizing error corresponding to a difference between the corrected data and a first evaluation value corresponding to the two-gradation image data; (4) diffusing the quantizing error to a plurality of pixels which have not yet been binary-coded and are located near the pixel of interest; and (5) varying the first evaluation value corresponding to the two-gradation image data indicative of the dot ON in accordance with the multi-gradation image data of the pixel of interest.
Inventors
- 👤 Toshiaki Kakutani
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 13:33
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/405; H04N1/4051; H04N1/4052
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
173 words
An image processing method for converting multi-gradation image data into two-gradation image data by employing an error diffusion method, the image processing method comprising the steps of: (1) adding a diffusion error derived from at least one pixel which has already been binary-coded and is located near a pixel of interest to multi-gradation image data of this pixel of interest to thereby obtain corrected data; (2) comparing the corrected data with a threshold value and converting the corrected data into two-gradation image data for indicating any one of a dot ON and a dot OFF; (3) calculating a quantizing error corresponding to a difference between the corrected data and a first evaluation value corresponding to the two-gradation image data; (4) diffusing the quantizing error to a plurality of pixels which have not yet been binary-coded and are located near the pixel of interest; and (5) varying the first evaluation value corresponding to the two-gradation image data indicative of the dot ON in accordance with the multi-gradation image data of the pixel of interest.
Claim 2
Dependent Claim
173 words
An image processing method for converting multi-gradation image data into two-gradation image data by employing an error diffusion method, the image processing method comprising the steps of: (1) adding a diffusion error derived from at least one pixel which has already been binary-coded and is located near a pixel of interest to multi-gradation image data of this pixel of interest to thereby obtain corrected data; (2) comparing the corrected data with a threshold value and converting the corrected data into two-gradation image data for indicating any one of a dot ON and a dot OFF; (3) calculating a quantizing error corresponding to a difference between the corrected data and a first evaluation value corresponding to the two-gradation image data; (4) diffusing the quantizing error to a plurality of pixels which have not yet been binary-coded and are located near the pixel of interest; and (5) varying the first evaluation value corresponding to the two-gradation image data indicative of the dot ON in accordance with the multi-gradation image data of the pixel of interest.
Claim 3
Dependent Claim
44 words
An image processing method as claimed in claim 1 wherein: when the multi-gradation image data of the pixel of interest represents low density, the first evaluation value is such a value indicative of density higher than maximum density represented by the multi-gradation image data.
Claim 4
Dependent Claim
33 words
An image processing method as claimed in claim 1 wherein: the lower the density indicated by the multi-gradation image data of the pixel of interest becomes, the greater the first evaluation value becomes.
Claim 5
Dependent Claim
38 words
An image processing method as claimed in claim 1 wherein: the first evaluation value is changed in response to a gamma characteristic owned by an image forming apparatus for forming an image by accepting the two-gradation image data.
Claim 6
Dependent Claim
79 words
An image processing method as claimed in claim 4 wherein: when a value of the multi-gradation image data of the pixel of interest is expressed as "Data", a gamma correction function equal to an inverse function of a gamma characteristic function of the image forming apparatus is expressed as "g(Data)", and the first evaluation value is expressed as "on -- value(Data)", on.sub.-- value(Data)=A×(Data/g(Data)), where symbol "A" is a gradation value of maximum density achieved by the multi-gradation image data.
Claim 7
Dependent Claim
31 words
An image processing method as claimed in claim 1, further comprising the step of: (6) changing the threshold value in response to the multi-gradation image data of the pixel of interest.
Claim 8
Dependent Claim
113 words
An image processing method as claimed in claim 6 wherein: when the threshold value is expressed by "thrld", a value of the multi-gradation image data of the pixel of interest is expressed by "Data", the first evaluation value is expressed by "on -- value (Data)", and a second evaluation value corresponding to the second gradation data indicative of the dot OFF is expressed by "off -- value(Data)", the threshold value "thrld" is varied in order to satisfy at least one of the following two conditions (a) and (b), namely: (a) when "Data" is a gradation value of low density, Data≦thrld≦(m+Data)/2; (b) when "Data" is a gradation value of high density, (m+Data)/2≦thrld≦Data, where: m=/2.
Claim 9
Dependent Claim
182 words
An image processing apparatus for converting multi-gradation data into two-gradation image data by employing an error diffusion method, comprising: a data correcting unit for adding a diffusion error derived from at least one pixel which has already been binary-coded and is located near a pixel of interest to multi-gradation image data of this pixel of interest to thereby obtain corrected data; a binary coding unit for comparing the corrected data with a threshold value and converting this compared data into two-gradation image data for indicating any one of a dot ON and a dot OFF; and an error calculating/diffusing unit for calculating a quantizing error corresponding to a difference between the corrected data and a first evaluation value corresponding to this two-gradation image data, and for diffusing the quantizing error to a plurality of pixels which have not yet been binary-coded and are located near the pixel of interest, wherein the error calculating/diffusing unit varies the first evaluation value corresponding to the two-gradation image data indicative of the dot ON in accordance with the multi-gradation image data of the pixel of interest.
Claim 10
Dependent Claim
182 words
An image processing apparatus for converting multi-gradation data into two-gradation image data by employing an error diffusion method, comprising: a data correcting unit for adding a diffusion error derived from at least one pixel which has already been binary-coded and is located near a pixel of interest to multi-gradation image data of this pixel of interest to thereby obtain corrected data; a binary coding unit for comparing the corrected data with a threshold value and converting this compared data into two-gradation image data for indicating any one of a dot ON and a dot OFF; and an error calculating/diffusing unit for calculating a quantizing error corresponding to a difference between the corrected data and a first evaluation value corresponding to this two-gradation image data, and for diffusing the quantizing error to a plurality of pixels which have not yet been binary-coded and are located near the pixel of interest, wherein the error calculating/diffusing unit varies the first evaluation value corresponding to the two-gradation image data indicative of the dot ON in accordance with the multi-gradation image data of the pixel of interest.
Claim 11
Dependent Claim
49 words
An image processing apparatus as claimed in claim 8 wherein: when the multi-gradation image data of the pixel of interest represents low density, the error calculating/diffusing unit sets the first evaluation value to such a value indicative of density higher than maximum density represented by the multi-gradation image data.
Claim 12
Dependent Claim
47 words
An image processing apparatus as claimed in claim 8 wherein: the error calculating/diffusing unit sets the first evaluation value in such a manner that the lower the density indicated by the multi-gradation image data of the pixel of interest becomes, the greater the first evaluation value becomes.
Claim 13
Dependent Claim
41 words
An image processing apparatus as claimed in claim 8 wherein: the error calculating/diffusing unit changes the first evaluation value in response to a gamma characteristic owned by an image forming apparatus for forming an image by accepting the two-gradation image data.
Claim 14
Dependent Claim
43 words
An image processing apparatus as claimed in claim 8, further comprising: a threshold value determining unit for determining the threshold value in such a manner that the threshold value is changed in response to the multi-gradation image data of the pixel of interest.
Claim 15
Dependent Claim
122 words
An image processing apparatus as claimed in claim 12 wherein: when the threshold value is expressed by "thrld", a value of the multi-gradation image data of the pixel of interest is expressed by "Data", the first evaluation value is expressed by "on -- value (Data)", and a second evaluation value corresponding to the second gradation data indicative of the dot OFF is expressed by "off -- value (Data)", the threshold value determining unit changes the threshold value "thrld" in order to satisfy at least one of the following two conditions (a) and (b), namely: (a) when "Data" is a gradation value of low density, Data≦thrld≦(m+Data)/2; (b) when "Data" is a gradation value of high density, (m+Data)/2≦thrld≦Data, where: m=(off -- value(Data)+on -- value(Data))/2.
Claim 16
Dependent Claim
206 words
A program medium for supplying a computer program to a computer, the computer program being used to execute an image processing method for converting multi-gradation image data into two-gradation image data by employing an error diffusing method by a computer, wherein: the computer holds such a program in a readable/understandable form, which causes the computer to execute the steps of: (1) adding a diffusion error derived from at least one pixel which has already been binary-coded and is located near a pixel of interest to multi-gradation image data of this pixel of interest to thereby obtain corrected data; (2) comparing the corrected data with a threshold value and converting this compared data into two-gradation image data for indicating any one of a dot ON and a dot OFF; (3) calculating a quantizing error corresponding to a difference between the corrected data and a first evaluation value corresponding to this two-gradation image data; (4) diffusing the quantizing error to a plurality of pixels which have not yet been binary-coded and are located near the pixel of interest; and (5) varying the first evaluation value corresponding to the two-gradation image data indicative of the dot ON in accordance with the multi-gradation image data of the pixel of interest.
Claim 17
Dependent Claim
206 words
A program medium for supplying a computer program to a computer, the computer program being used to execute an image processing method for converting multi-gradation image data into two-gradation image data by employing an error diffusing method by a computer, wherein: the computer holds such a program in a readable/understandable form, which causes the computer to execute the steps of: (1) adding a diffusion error derived from at least one pixel which has already been binary-coded and is located near a pixel of interest to multi-gradation image data of this pixel of interest to thereby obtain corrected data; (2) comparing the corrected data with a threshold value and converting this compared data into two-gradation image data for indicating any one of a dot ON and a dot OFF; (3) calculating a quantizing error corresponding to a difference between the corrected data and a first evaluation value corresponding to this two-gradation image data; (4) diffusing the quantizing error to a plurality of pixels which have not yet been binary-coded and are located near the pixel of interest; and (5) varying the first evaluation value corresponding to the two-gradation image data indicative of the dot ON in accordance with the multi-gradation image data of the pixel of interest.
Claim 18
Dependent Claim
39 words
A program medium as claimed in claim 14, further comprising: a program used to cause the computer to execute: (6) a step for changing the threshold value in response to the multi-gradation image data of the pixel of interest.
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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) | 2001-05-04 | 2001-11-03 | 2002-05-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-05-04 | 2005-11-03 | 2006-05-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-05-04 | 2009-11-03 | 2010-05-05 | $7700.00 | Window Closed / Lapsed |