US6721458B1 — Artifact reduction using adaptive nonlinear filte…

Claim 1

Independent Claim 125 words

A method for producing an output representation of a mixed-mode document with reduced artifacts, comprising: for each of a plurality of pixels representing the document, computing a first average gray scale value of a first pixel neighborhood and a second average gray scale value of a second pixel neighborhood that overlaps the first pixel neighborhood; comparing the difference between the computed first average gray scale value and a value of that pixel with a predetermined threshold value; and based on the result of the comparison, applying either a median filter to the first pixel neighborhood, a first low-pass filter to the second pixel neighborhood, or a second low-pass filter to the first pixel neighborhood, to produce an output representation of the document with reduced artifacts.

Claim 2

Independent Claim 125 words

A method for producing an output representation of a mixed-mode document with reduced artifacts, comprising: for each of a plurality of pixels representing the document, computing a first average gray scale value of a first pixel neighborhood and a second average gray scale value of a second pixel neighborhood that overlaps the first pixel neighborhood; comparing the difference between the computed first average gray scale value and a value of that pixel with a predetermined threshold value; and based on the result of the comparison, applying either a median filter to the first pixel neighborhood, a first low-pass filter to the second pixel neighborhood, or a second low-pass filter to the first pixel neighborhood, to produce an output representation of the document with reduced artifacts.

Claim 3

Dependent Claim 18 words

The method of claim 1 , wherein the pixel representation of the mixed-mode document is a high-resolution representation.

Claim 4

Dependent Claim 18 words

The method of claim 1 , wherein the second pixel neighborhood is larger than the first pixel neighborhood.

Claim 5

Dependent Claim 39 words

The method of claim 1 , wherein the median filter is applied if the difference between the computed first average gray scale value and the value of that pixel is greater than or equal to the predetermined threshold value.

Claim 6

Dependent Claim 63 words

The method of claim 4 , wherein either the first low-pass filter or the second low-pass filter is applied based on a comparison between (i) the difference between the computed first average gray scale value and a gray scale value of that pixel and (ii) the difference between the computed second average gray scale value and the gray scale value of that pixel.

Claim 7

Dependent Claim 43 words

The method of claim 5 , wherein the first low-pass filter is represented by a weighted average gray scale value of the second pixel neighborhood, and the second low-pass filter is represented by an average gray scale value of the first pixel neighborhood.

Claim 8

Dependent Claim 47 words

The method of claim 1 , wherein the first average gray scale value is computed on a 3×3 neighborhood of pixels, centered on but excluding that pixel, and the second average gray scale value is computed on a 3×5 neighborhood centered on and double weighting that pixel.

Claim 9

Independent Claim 143 words

A method for producing an output representation of mixed-mode document with reduced artifacts, comprising: for each of a plurality of pixels representing the document, computing a first average gray scale value of a first pixel neighborhood and a second average gray scale value of a second pixel neighborhood that overlaps the first pixel neighborhood; comparing the difference between the computed first average gray scale value and a value of that pixel with a predetermined threshold value; and based on the result of the comparison, applying either a first filter kernel to the first pixel neighborhood, a second filter kernel to the first pixel neighborhood, a third filter kernel to the first pixel neighborhood, a first low-pass filter to the second pixel neighborhood, or a second low-pass filter to the first pixel neighborhood, to produce an output representation of the document with reduced artifacts.

Claim 10

Independent Claim 143 words

A method for producing an output representation of mixed-mode document with reduced artifacts, comprising: for each of a plurality of pixels representing the document, computing a first average gray scale value of a first pixel neighborhood and a second average gray scale value of a second pixel neighborhood that overlaps the first pixel neighborhood; comparing the difference between the computed first average gray scale value and a value of that pixel with a predetermined threshold value; and based on the result of the comparison, applying either a first filter kernel to the first pixel neighborhood, a second filter kernel to the first pixel neighborhood, a third filter kernel to the first pixel neighborhood, a first low-pass filter to the second pixel neighborhood, or a second low-pass filter to the first pixel neighborhood, to produce an output representation of the document with reduced artifacts.

Claim 11

Dependent Claim 18 words

The method of claim 8 , wherein the pixel representation of the mixed-mode document is a low-resolution representation.

Claim 12

Dependent Claim 38 words

The method of claim 8 , wherein the first filter kernel is weighted to preserve horizontal and vertical edges in the output representation, and the second filter kernel is weighted to preserve slanted edges in the output representation.

Claim 13

Dependent Claim 79 words

The method of claim 10 , wherein either the first, second or third filter kernels is applied if the difference between the computed first average gray scale value and the value of that pixel is greater than or equal to the predetermined threshold value, and wherein either the first or second low-pass filter is applied if the difference between the computed first average gray scale value and the value of that pixel is less than the predetermined threshold value.

Claim 14

Dependent Claim 73 words

The method of claim 11 , wherein the first filter kernel is applied if a first sub-condition, indicating that horizontal and vertical edges are to be preserved, is satisfied, the second filter kernel is applied if the first sub-condition is not satisfied but a second sub-condition, indicating that slanted edges are to be preserved, is satisfied, and the third filter kernel is applied if neither the first nor the second sub-condition is satisfied.

Claim 15

Dependent Claim 58 words

The method of claim 12 , wherein the first low-pass filter, represented by a weighted average gray scale value of the second pixel neighborhood, is applied if the second sub-condition is satisfied, and the second low-pass filter, represented by an average gray scale value of the first pixel neighborhood, is applied if the second sub-condition is not satisfied.

Claim 16

Independent Claim 167 words

An apparatus for receiving an input signal conveying a mixed-mode document and, in response thereto, generating an output signal reproducing the mixed-mode document in a form having reduced artifacts, the apparatus comprising: a filter device including a median filter, a first low-pass filter, and a second low-pass filter; an analyzer that receives the input signal, computes, for each of a plurality of pixels representing the document, a first average gray scale value of a first pixel neighborhood and a second average gray scale value of a second pixel neighborhood that overlaps the first pixel neighborhood, compares the difference between the computed first average gray scale value and a value of that pixel with a predetermined threshold value, and outputs a signal indicative of the comparison; and a filter control that receives the comparison signal from the analyzer, and outputs a control signal to the filter device to apply either the median filter or a selected one of the low-pass filters based on the result of the comparison.

Claim 17

Independent Claim 167 words

An apparatus for receiving an input signal conveying a mixed-mode document and, in response thereto, generating an output signal reproducing the mixed-mode document in a form having reduced artifacts, the apparatus comprising: a filter device including a median filter, a first low-pass filter, and a second low-pass filter; an analyzer that receives the input signal, computes, for each of a plurality of pixels representing the document, a first average gray scale value of a first pixel neighborhood and a second average gray scale value of a second pixel neighborhood that overlaps the first pixel neighborhood, compares the difference between the computed first average gray scale value and a value of that pixel with a predetermined threshold value, and outputs a signal indicative of the comparison; and a filter control that receives the comparison signal from the analyzer, and outputs a control signal to the filter device to apply either the median filter or a selected one of the low-pass filters based on the result of the comparison.

Claim 18

Dependent Claim 58 words

The apparatus of claim 14 , wherein the filter control outputs a control signal to the filter device to apply the median filter if the signal received from the analyzer indicates that the difference between the computed first average gray scale value and the value of that pixel is greater than or equal to the predetermined threshold value.

Claim 19

Dependent Claim 83 words

The apparatus of claim 15 , wherein the analyzer further compares (i) the difference between the computed first average gray scale value and a gray scale value of that pixel and (ii) the difference between the computed second average gray scale value and the gray scale value of that pixel, and wherein the filter control outputs a control signal to the filter device to apply either the first low-pass filter or the second low-pass filter based on the result of the further comparison.

Claim 20

Dependent Claim 43 words

The apparatus of claim 16 , wherein the first low-pass filter is represented by a weighted average gray scale value of the second pixel neighborhood, and the second low-pass filter is represented by an average gray scale value of the first pixel neighborhood.

Claim 21

Dependent Claim 47 words

The apparatus of claim 14 , wherein the first average gray scale value is computed on a 3×3 neighborhood of pixels, centered on but excluding that pixel, and the second average gray scale value is computed on a 3×5 neighborhood centered on and double weighting that pixel.

Claim 22

Independent Claim 180 words

An apparatus for receiving an input signal conveying a mixed-mode document and, in response thereto, generating an output signal reproducing the mixed-mode document in a form having reduced artifacts, the apparatus comprising: a filter device including a first filter kernel, a second filter kernel, a third filter kernel, a first low-pass filter, and a second low-pass filter; an analyzer that receives the input signal, computes, for each of a plurality of pixels representing the document, a first average gray scale value of a first pixel neighborhood and a second average gray scale value of a second pixel neighborhood that overlaps the first pixel neighborhood, larger than the first pixel neighborhood, compares the difference between the computed first average gray scale value and a value of that pixel with a predetermined threshold value, and outputs a signal indicative of the comparison; and a filter control that receives the comparison signal from the analyzer, and outputs a control signal to the filter device to apply a selected one of the filter kernels or low-pass filters based on the result of the comparison.

Claim 23

Independent Claim 180 words

An apparatus for receiving an input signal conveying a mixed-mode document and, in response thereto, generating an output signal reproducing the mixed-mode document in a form having reduced artifacts, the apparatus comprising: a filter device including a first filter kernel, a second filter kernel, a third filter kernel, a first low-pass filter, and a second low-pass filter; an analyzer that receives the input signal, computes, for each of a plurality of pixels representing the document, a first average gray scale value of a first pixel neighborhood and a second average gray scale value of a second pixel neighborhood that overlaps the first pixel neighborhood, larger than the first pixel neighborhood, compares the difference between the computed first average gray scale value and a value of that pixel with a predetermined threshold value, and outputs a signal indicative of the comparison; and a filter control that receives the comparison signal from the analyzer, and outputs a control signal to the filter device to apply a selected one of the filter kernels or low-pass filters based on the result of the comparison.

Claim 24

Dependent Claim 38 words

The apparatus of claim 19 , wherein the first filter kernel is weighted to preserve horizontal and vertical edges in the output representation, and the second filter kernel is weighted to preserve slanted edges in the output representation.

Claim 25

Dependent Claim 117 words

The apparatus of claim 20 , wherein the filter control outputs a control signal to the filter device to apply either the first, second or third filter kernels if the signal received from the analyzer indicates that the difference between the computed first average gray scale value and the value of that pixel is greater than or equal to the predetermined threshold value, and wherein the filter control outputs a control signal to the filter device to apply either the first or second low-pass filter if the signal received from the analyzer indicates that the difference between the computed first average gray scale value and the value of that pixel is less than the predetermined threshold value.

Claim 26

Dependent Claim 73 words

The apparatus of claim 21 , wherein the first filter kernel is applied if a first sub-condition, indicating that horizontal and vertical edges are to be preserved, is satisfied, the second filter kernel is applied if the first sub-condition is not satisfied but a second sub-condition, indicating that slanted edges are to be preserved, is satisfied, and the third filter kernel is applied if neither the first nor the second sub-condition is satisfied.

Claim 27

Dependent Claim 58 words

The apparatus of claim 22 , wherein the first low-pass filter, represented by a weighted average gray scale value of the second pixel neighborhood, is applied if the second sub-condition is satisfied, and the second low-pass filter, represented by an average gray scale value of the first pixel neighborhood, is applied if the second sub-condition is not satisfied.

Claim 28

Dependent Claim 145 words

A machine-readable medium embodying a program of instructions for causing a machine to perform a method of producing an output representation of a mixed-mode document with reduced artifacts, the program of instructions comprising instructions for: computing, for each of a plurality of pixels representing the document, a first average gray scale value of a first pixel neighborhood and a second average gray scale value of a second pixel neighborhood that overlaps the first pixel neighborhood; comparing the difference between the computed first average gray scale value and a value of that pixel with a predetermined threshold value; and applying, based on the result of the comparison, either a median filter to the first pixel neighborhood, a first low-pass filter to the second pixel neighborhood, or a second low-pass filter to the first pixel neighborhood, to produce an output representation of the document with reduced artifacts.

Claim 29

Dependent Claim 145 words

A machine-readable medium embodying a program of instructions for causing a machine to perform a method of producing an output representation of a mixed-mode document with reduced artifacts, the program of instructions comprising instructions for: computing, for each of a plurality of pixels representing the document, a first average gray scale value of a first pixel neighborhood and a second average gray scale value of a second pixel neighborhood that overlaps the first pixel neighborhood; comparing the difference between the computed first average gray scale value and a value of that pixel with a predetermined threshold value; and applying, based on the result of the comparison, either a median filter to the first pixel neighborhood, a first low-pass filter to the second pixel neighborhood, or a second low-pass filter to the first pixel neighborhood, to produce an output representation of the document with reduced artifacts.

Claim 30

Dependent Claim 19 words

The machine-readable medium of claim 24 , wherein the pixel representation of the mixed-mode document is a high-resolution representation.

Claim 31

Dependent Claim 19 words

The machine-readable medium of claim 24 , wherein the second pixel neighborhood is larger than the first pixel neighborhood.

Claim 32

Dependent Claim 40 words

The machine-readable medium of claim 24 , wherein the median filter is applied if the difference between the computed first average gray scale value and the value of that pixel is greater than or equal to the predetermined threshold value.

Claim 33

Dependent Claim 64 words

The machine-readable medium of claim 27 , wherein either the first low-pass filter or the second low-pass filter is applied based on a comparison between (i) the difference between the computed first average gray scale value and a gray scale value of that pixel and (ii) the difference between the computed second average gray scale value and the gray scale value of that pixel.

Claim 34

Dependent Claim 44 words

The machine-readable medium of claim 28 , wherein the first low-pass filter is represented by a weighted average gray scale value of the second pixel neighborhood, and the second low-pass filter is represented by an average gray scale value of the first pixel neighborhood.

Claim 35

Dependent Claim 48 words

The machine-readable medium of claim 24 , wherein the first average gray scale value is computed on a 3×3 neighborhood of pixels, centered on but excluding that pixel, and the second average gray scale value is computed on a 3×5 neighborhood centered on and double weighting that pixel.

Claim 36

Dependent Claim 164 words

A machine-readable medium embodying a program of instructions for causing a machine to perform a method of producing an output representation of a mixed-mode document with reduced artifacts, the program of instructions comprising instructions for: computing, for each of a plurality of pixels representing the document, a first average gray scale value of a first pixel neighborhood and a second average gray scale value of a second pixel neighborhood that overlaps the first pixel neighborhood; comparing the difference between the computed first average gray scale value and a value of that pixel with a predetermined threshold value; and applying, based on the result of the comparison, either a first filter kernel to the first pixel neighborhood, a second filter kernel to the first pixel neighborhood, a third filter kernel to the first pixel neighborhood, a first low-pass filter to the second pixel neighborhood, or a second low-pass filter to the first pixel neighborhood, to produce an output representation of the document with reduced artifacts.

Claim 37

Dependent Claim 164 words

A machine-readable medium embodying a program of instructions for causing a machine to perform a method of producing an output representation of a mixed-mode document with reduced artifacts, the program of instructions comprising instructions for: computing, for each of a plurality of pixels representing the document, a first average gray scale value of a first pixel neighborhood and a second average gray scale value of a second pixel neighborhood that overlaps the first pixel neighborhood; comparing the difference between the computed first average gray scale value and a value of that pixel with a predetermined threshold value; and applying, based on the result of the comparison, either a first filter kernel to the first pixel neighborhood, a second filter kernel to the first pixel neighborhood, a third filter kernel to the first pixel neighborhood, a first low-pass filter to the second pixel neighborhood, or a second low-pass filter to the first pixel neighborhood, to produce an output representation of the document with reduced artifacts.

Claim 38

Dependent Claim 19 words

The machine-readable medium of claim 31 , wherein the pixel representation of the mixed-mode document is a low-resolution representation.

Claim 39

Dependent Claim 39 words

The machine-readable medium of claim 31 , wherein the first filter kernel is weighted to preserve horizontal and vertical edges in the output representation, and the second filter kernel is weighted to preserve slanted edges in the output representation.

Claim 40

Dependent Claim 80 words

The machine-readable medium of claim 33 , wherein either the first, second or third filter kernels is applied if the difference between the computed first average gray scale value and the value of that pixel is greater than or equal to the predetermined threshold value, and wherein either the first or second low-pass filter is applied if the difference between the computed first average gray scale value and the value of that pixel is less than the predetermined threshold value.

Claim 41

Dependent Claim 74 words

The machine-readable medium of claim 34 , wherein the first filter kernel is applied if a first sub-condition, indicating that horizontal and vertical edges are to be preserved, is satisfied, the second filter kernel is applied if the first sub-condition is not satisfied but a second sub-condition, indicating that slanted edges are to be preserved, is satisfied, and the third filter kernel is applied if neither the first nor the second sub-condition is satisfied.

Claim 42

Dependent Claim 59 words

The machine-readable medium of claim 35 , wherein the first low-pass filter, represented by a weighted average gray scale value of the second pixel neighborhood, is applied if the second sub-condition is satisfied, and the second low-pass filter, represented by an average gray scale value of the first pixel neighborhood, is applied if the second sub-condition is not satisfied.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2007-04-13	2007-10-13	2008-04-13	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2011-04-13	2011-10-13	2012-04-13	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2015-04-13	2015-10-13	2016-04-13	$7700.00	Window Closed / Lapsed

Artifact reduction using adaptive nonlinear filters

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