US5363209A
Expired / Lapsed
US
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Image-dependent sharpness enhancement
Assignee: Xerox Corp
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Filing: 1993-11-05
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Granted: 1994-11-08
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Expires: 2013-11-05
Abstract
Abstract A method of altering the sharpness in the reproduction of an electronically encoded natural scene image, including process steps of: a) converting the signals to a luminance-chrominance signal format, wherein at least one signal represents overall image intensity; b) determining the maximum local contrast within the image; c) determining a filter function applicable to the image which increases maximum local contrast to a predetermined target value, and all other contrast to an amount proportional thereto; and d) applying the determined filter function to the image to increase sharpness thereof.
Inventors
- 👤 Reiner Eschbach
- 👤 William A. Fuss
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 01:36
CPC Classifications
G; G06; G06T; G06T5/00; G06T5/20; H; H04; H04N; H04N1/00; H04N1/46; H04N1/56; H04N1/58
Claims Analysis
Total Claims: 45
Claim 1
Independent Claim
170 words
Apparatus for altering the sharpness in the reproduction of an electronically encoded natural scene image, comprising: a) an electronic signal input suitable for receiving an electronically encoded natural scene image, where the encoding is in terms of color density signals; b) a color space conversion circuit, converting the color density signals to a format wherein at least one signal represents image intensity and is defined for L levels of intensity; c) a comparator iteratively comparing intensity signals for a predetermined area of the image to determine a measure of sharpness of the image and producing an output signal indicative thereof. d) a sharpness filter coefficient deriving circuit, having an external signal input receiving desired sharpness signals from a user, and deriving filter coefficients as a function of the comparator output signals and desired sharpness; e) a sharpness filter, operating on one of the color density encoded image signals or converted color density signals, to sharpen the image; f) returning the image to an output encoding, if required, preparatory to output.
Claim 2
Dependent Claim
170 words
Apparatus for altering the sharpness in the reproduction of an electronically encoded natural scene image, comprising: a) an electronic signal input suitable for receiving an electronically encoded natural scene image, where the encoding is in terms of color density signals; b) a color space conversion circuit, converting the color density signals to a format wherein at least one signal represents image intensity and is defined for L levels of intensity; c) a comparator iteratively comparing intensity signals for a predetermined area of the image to determine a measure of sharpness of the image and producing an output signal indicative thereof. d) a sharpness filter coefficient deriving circuit, having an external signal input receiving desired sharpness signals from a user, and deriving filter coefficients as a function of the comparator output signals and desired sharpness; e) a sharpness filter, operating on one of the color density encoded image signals or converted color density signals, to sharpen the image; f) returning the image to an output encoding, if required, preparatory to output.
Claim 3
Dependent Claim
21 words
The apparatus of claim 1 wherein the measure of sharpness is given by a maximum local sharpness measured for the image.
Claim 4
Dependent Claim
23 words
The apparatus of claim 2 wherein the maximum local measure of sharpness is given by maximum local contrast over a small image window.
Claim 5
Dependent Claim
16 words
The apparatus of claim 3 wherein the window is given by the relative pixel positions {(-1,0),(0,-1)}.
Claim 6
Dependent Claim
16 words
The apparatus of claim 3 wherein the window is given by the relative pixel positions {(-1,-1),(-1,0),(-1,1),(0,-1)}.
Claim 7
Dependent Claim
23 words
The apparatus as defined in claim 1 including the additional step of modifying sharpness as a function of a plurality of sharpness measurements.
Claim 8
Dependent Claim
20 words
The apparatus as defined in claim 1 wherein color density signals are in terms of red, green and blue colors.
Claim 9
Dependent Claim
15 words
The apparatus as defined in claim 1 wherein image intensity is in terms of luminance.
Claim 10
Independent Claim
142 words
A method of altering the sharpness in the reproduction of an electronically encoded natural scene image, comprising the steps of: a) receiving an electronically encoded natural scene image, where the original encoding is in terms of color density signals; b) converting the color density signals to a format wherein at least one signal represents image intensity and is defined for L levels of intensity; c) comparing intensity signals for a predetermined area of the image to determine a maximum local measurement of sharpness for the image; d) using determined maximum local area sharpness measurement as an input to a look-up table in device memory, to retrieve predetermined filter coefficient values mapped to said maximum local area sharpness measurement; e) filtering the color density signals with a sharpness filter operating in accordance with the predetermined filter coefficient values to derive a sharpened image.
Claim 11
Independent Claim
142 words
A method of altering the sharpness in the reproduction of an electronically encoded natural scene image, comprising the steps of: a) receiving an electronically encoded natural scene image, where the original encoding is in terms of color density signals; b) converting the color density signals to a format wherein at least one signal represents image intensity and is defined for L levels of intensity; c) comparing intensity signals for a predetermined area of the image to determine a maximum local measurement of sharpness for the image; d) using determined maximum local area sharpness measurement as an input to a look-up table in device memory, to retrieve predetermined filter coefficient values mapped to said maximum local area sharpness measurement; e) filtering the color density signals with a sharpness filter operating in accordance with the predetermined filter coefficient values to derive a sharpened image.
Claim 12
Dependent Claim
21 words
The method of claim 9 wherein the measure of sharpness is given by a maximum local sharpness measured for the image.
Claim 13
Dependent Claim
23 words
The method of claim 10 wherein the maximum local measure of sharpness is given by maximum local contrast over a small image window.
Claim 14
Dependent Claim
16 words
The method of claim 11 wherein the window is given by the relative pixel positions {(-1,0),(0,-1)}.
Claim 15
Dependent Claim
16 words
The method of claim 11 wherein the window is given by the relative pixel positions {(-1,-1),(-1,0),(-1,1),(0,-1)}.
Claim 16
Dependent Claim
23 words
The method as defined in claim 9 including the additional step of modifying sharpness as a function of a plurality of sharpness measurements.
Claim 17
Dependent Claim
25 words
The method as defined in claim 9 wherein the filter is derived using the measured sharpness and a desired sharpness using an idealized image edge.
Claim 18
Dependent Claim
29 words
The method as defined in claim 9 including the additional step of modifying maximum local area sharpness as a function of a plurality of maximum local area sharpness measurements.
Claim 19
Dependent Claim
20 words
The method as defined in claim 9 wherein color density signals are in terms of red, green and blue colors.
Claim 20
Dependent Claim
15 words
The method as defined in claim 9 wherein image intensity is in terms of luminance.
Claim 21
Dependent Claim
158 words
Apparatus for altering the sharpness in the reproduction of an electronically encoded natural scene image, comprising: a) an electronic signal input suitable for receiving an electronically encoded natural scene image, where the encoding is in terms of color density signals; b) a color space conversion circuit, converting the color density signals to a format wherein at least one signal represents image intensity and is defined for L levels of intensity; c) a comparator comparing intensity signals for a predetermined area of the image to determine a measurement of sharpness and producing an output signal indicative of the determined sharpness for the image; d) a sharpness filter coefficient memory, addressable by values derived at the comparator to retrieve predetermined filter coefficient values mapped to said maximum local area sharpness measurement; e) a sharpness filter, operating with the retrieved filter coefficient values on one of the color density encoded image signals or converted color density signals, to sharpen the image.
Claim 22
Dependent Claim
158 words
Apparatus for altering the sharpness in the reproduction of an electronically encoded natural scene image, comprising: a) an electronic signal input suitable for receiving an electronically encoded natural scene image, where the encoding is in terms of color density signals; b) a color space conversion circuit, converting the color density signals to a format wherein at least one signal represents image intensity and is defined for L levels of intensity; c) a comparator comparing intensity signals for a predetermined area of the image to determine a measurement of sharpness and producing an output signal indicative of the determined sharpness for the image; d) a sharpness filter coefficient memory, addressable by values derived at the comparator to retrieve predetermined filter coefficient values mapped to said maximum local area sharpness measurement; e) a sharpness filter, operating with the retrieved filter coefficient values on one of the color density encoded image signals or converted color density signals, to sharpen the image.
Claim 23
Dependent Claim
21 words
The apparatus of claim 19 wherein the measure of sharpness is given by a maximum local sharpness measured for the image.
Claim 24
Dependent Claim
23 words
The apparatus of claim 20 wherein the maximum local measure of sharpness is given by maximum local contrast over a small image window.
Claim 25
Dependent Claim
16 words
The apparatus of claim 21 wherein the window is given by the relative pixel positions {(-1,0),(0,-1)}.
Claim 26
Dependent Claim
16 words
The apparatus of claim 22 wherein the window is given by the relative pixel positions {(-1,-1),(-1,0),(-1,1),(0,-1)}.
Claim 27
Dependent Claim
29 words
The apparatus as defined in claim 19 including a sharpness modification circuit, modifying maximum local area sharpness as a function of a plurality of maximum local area sharpness measurements.
Claim 28
Dependent Claim
20 words
The method as defined in claim 19 wherein color density signals are in terms of red, green and blue colors.
Claim 29
Dependent Claim
15 words
The method as defined in claim 19 wherein image intensity is in terms of luminance.
Claim 30
Dependent Claim
169 words
Apparatus for altering the sharpness in the reproduction of an electronically encoded natural scene image, comprising: a) an electronic signal input suitable for receiving an electronically encoded natural scene image, where the encoding is in terms of k-bit color density signals; b) a color space conversion circuit, converting the color density signals to a format wherein at least one signal represents image intensity and is defined for L levels of intensity; c) a comparator comparing intensity signals for a predetermined area of the image to determine a measurement of sharpness and producing an output signal indicative thereof for the image; d) a enhancement factor memory, addressable by values derived at the comparator to retrieve predetermined enhancement factor values mapped to said maximum local area sharpness measurement; e) an error diffusion circuit, comparing color density signals to a threshold, said threshold set for each pixel as a function of the retrieved enhancement factor, said circuit providing as an output I-bit color density signals, where I<k and the image is sharpened.
Claim 31
Dependent Claim
169 words
Apparatus for altering the sharpness in the reproduction of an electronically encoded natural scene image, comprising: a) an electronic signal input suitable for receiving an electronically encoded natural scene image, where the encoding is in terms of k-bit color density signals; b) a color space conversion circuit, converting the color density signals to a format wherein at least one signal represents image intensity and is defined for L levels of intensity; c) a comparator comparing intensity signals for a predetermined area of the image to determine a measurement of sharpness and producing an output signal indicative thereof for the image; d) a enhancement factor memory, addressable by values derived at the comparator to retrieve predetermined enhancement factor values mapped to said maximum local area sharpness measurement; e) an error diffusion circuit, comparing color density signals to a threshold, said threshold set for each pixel as a function of the retrieved enhancement factor, said circuit providing as an output I-bit color density signals, where I<k and the image is sharpened.
Claim 32
Dependent Claim
21 words
The method of claim 27 wherein the measure of sharpness is given by a maximum local sharpness measured for the image.
Claim 33
Dependent Claim
23 words
The method of claim 28 wherein the maximum local measure of sharpness is given by maximum local contrast over a small image window.
Claim 34
Dependent Claim
16 words
The method of claim 29 wherein the window is given by the relative pixel positions {(-1,0),(0,-1)}.
Claim 35
Dependent Claim
16 words
The method of claim 29 wherein the window is given by the relative pixel positions {(-1,-1),(-1,0),(-1,1),(0,-1)}.
Claim 36
Dependent Claim
29 words
The apparatus as defined in claim 27 including a sharpness modification circuit, modifying maximum local area sharpness as a function of a plurality of maximum local area sharpness measurements.
Claim 37
Dependent Claim
20 words
The method as defined in claim 27 wherein color density signals are in terms of red, green and blue colors.
Claim 38
Dependent Claim
15 words
The method as defined in claim 27 wherein image intensity is in terms of luminance.
Claim 39
Independent Claim
151 words
A method of altering the sharpness in the reproduction of an electronically encoded natural scene image, comprising the steps of: a) receiving an electronically encoded natural scene image, where the original encoding is in terms of k-bit color density signals; b) converting the color density signals to a format wherein at least one signal represents image intensity and is defined for L levels of intensity; c) comparing intensity signals for a predetermined area of the image to determine a maximum local area measurement of sharpness for the image; d) retrieving from an enhancement factor memory predetermined enhancement factor values using as an address to said memory said maximum local area sharpness measurement; e) halftoning the color density signals with a threshold, said threshold set for each pixel as a function of the retrieved enhancement factor, and providing as an output l-bit color density signals, where I<k and the image is sharpened.
Claim 40
Independent Claim
151 words
A method of altering the sharpness in the reproduction of an electronically encoded natural scene image, comprising the steps of: a) receiving an electronically encoded natural scene image, where the original encoding is in terms of k-bit color density signals; b) converting the color density signals to a format wherein at least one signal represents image intensity and is defined for L levels of intensity; c) comparing intensity signals for a predetermined area of the image to determine a maximum local area measurement of sharpness for the image; d) retrieving from an enhancement factor memory predetermined enhancement factor values using as an address to said memory said maximum local area sharpness measurement; e) halftoning the color density signals with a threshold, said threshold set for each pixel as a function of the retrieved enhancement factor, and providing as an output l-bit color density signals, where I<k and the image is sharpened.
Claim 41
Dependent Claim
21 words
The method of claim 35 wherein the measure of sharpness is given by a maximum local sharpness measured for the image.
Claim 42
Dependent Claim
23 words
The method of claim 36 wherein the maximum local measure of sharpness is given by maximum local contrast over a small image window.
Claim 43
Dependent Claim
16 words
The method of claim 37 wherein the window is given by the relative pixel positions {(-1,0),(0,-1)}.
Claim 44
Dependent Claim
16 words
The method of claim 37 wherein the window is given by the relative pixel positions {(-1,-1),(-1,0),(-1,1),(0,-1)}.
Claim 45
Dependent Claim
17 words
The method of claim 35 wherein the halftoning method used is an edge enhanced error diffusion process.
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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) | 1997-11-07 | 1998-05-09 | 1998-11-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-11-07 | 2002-05-09 | 2002-11-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-11-07 | 2006-05-09 | 2006-11-08 | $7700.00 | Window Closed / Lapsed |