Patent US6608942B1 successfully refreshed from Google Patents.
US6608942B1
Expired / Lapsed
US
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Method for smoothing jagged edges in digital images
Assignee: Canon Inc
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Filing: 1999-01-12
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Granted: 2003-08-19
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Expires: 2019-01-12
Abstract
Abstract A method of smoothing jagged edges in graphical data. The method detects one or more edge of a selected pixel in the graphical data, dependent upon intensities of the selected pixel and another pixel surrounding a respective site of one or more edges and predetermied gradients of at least the selected pixel and the respective site surrounding the pixel. An adapted convolution mask is applied to the selected pixel and a predetermined neighborhood of pixels containing the selected pixel. The coefficient values of the convolution mask are dependent upon one or more detected edges.
Inventors
- 👤 Delphine Anh Dao Le
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 11:02
CPC Classifications
G; G06; G06T; G06T5/00; G06T5/70; G06T5/20; G06T5/30; G06T7/00; G06T7/10; G06T7/13; G06K; G06K2215/00; G06K2215/0002; G06K2215/0062; G06K2215/0071; G06K2215/0074; G06T2200/00; G06T2200/12; G06T2207/00; G06T2207/20; G06T2207/20172; G06T2207/20192
Claims Analysis
Total Claims: 88
Claim 1
Independent Claim
142 words
A method of smoothing jagged edges of oblique lines or curves in a digital image, said method comprising the steps of: detecting one or more edges of a selected pixel in the digital image, wherein a candidate edge of the selected pixel for detection is detected dependent upon intensities of the selected pixel and a further pixel abutting the candidate edge of the selected pixel, predetermined gradients of at least the selected pixel and the further pixel, and predetermined gradients of one or more pixels diagonally adjacent the selected pixel; and modifying the selected pixel by applying a convolution mask to the selected pixel and a predetermined neighbourhood of pixels containing the selected pixel so as to smooth oblique edges without blurring horizontal or vertical edges, wherein coefficient values of the convolution mask are dependent upon the one or more detected edges.
Claim 2
Independent Claim
142 words
A method of smoothing jagged edges of oblique lines or curves in a digital image, said method comprising the steps of: detecting one or more edges of a selected pixel in the digital image, wherein a candidate edge of the selected pixel for detection is detected dependent upon intensities of the selected pixel and a further pixel abutting the candidate edge of the selected pixel, predetermined gradients of at least the selected pixel and the further pixel, and predetermined gradients of one or more pixels diagonally adjacent the selected pixel; and modifying the selected pixel by applying a convolution mask to the selected pixel and a predetermined neighbourhood of pixels containing the selected pixel so as to smooth oblique edges without blurring horizontal or vertical edges, wherein coefficient values of the convolution mask are dependent upon the one or more detected edges.
Claim 3
Dependent Claim
31 words
The method according to claim 1 , wherein the detecting step is dependent upon a difference between the intensities of the selected pixel and the further pixel satisfying an intensity threshold.
Claim 4
Dependent Claim
24 words
The method according to claim 2 , wherein the detecting step is dependent upon an absolute value of the difference exceeding the intensity threshold.
Claim 5
Dependent Claim
29 words
The method according to claim 1 , wherein the detecting step is dependent upon the predetermined gradients of the selected pixel and the further pixel satisfying a gradient threshold.
Claim 6
Dependent Claim
35 words
The method according to claim 4 , wherein the predetermined gradients of the selected pixel and the further pixel are either vertical or horizontal dependent upon the candidate edge being either horizontal or vertical, respectively.
Claim 7
Dependent Claim
25 words
The method according to claim 4 , wherein the predetermined gradients of the selected pixel and the further pixel are greater than the gradient threshold.
Claim 8
Dependent Claim
25 words
The method according to claim 4 , wherein the predetermined gradients of the selected pixel and the further pixel are less than the gradient threshold.
Claim 9
Dependent Claim
25 words
The method according to claim 1 , wherein the detecting step is dependent upon the predetermined gradients of the diagonal pixels satisfying a gradient threshold.
Claim 10
Dependent Claim
39 words
The method according to claim 8 , wherein: the predetermined gradients of the selected pixel and the further pixel are greater than the gradient threshold; and the predetermined gradients of the diagonal pixels are less than the gradient threshold.
Claim 11
Dependent Claim
39 words
The method according to claim 8 , wherein: the predetermined gradients of the selected pixel and the further pixel are less than the gradient threshold; and the predetermined gradients of the diagonal pixels are greater than the gradient threshold.
Claim 12
Dependent Claim
38 words
The method according to claim 1 , wherein if a single edge is detected, one or more coefficient values of a portion of the convolution mask next to the detected single edge are set to a predetermined value.
Claim 13
Dependent Claim
13 words
The method according to claim 11 , wherein the predetermined value is zero.
Claim 14
Dependent Claim
38 words
The method according to claim 1 , wherein if a double edge is detected, one or more coefficient values of each portion of the convolution mask next to the detected double edge are set to a predetermined value.
Claim 15
Dependent Claim
13 words
The method according to claim 13 , wherein the predetermined value is zero.
Claim 16
Dependent Claim
128 words
The method according to claim 6 or 7 , wherein the detecting step comprises the sub-steps of: a first detecting sub-step, of detecting a double edge, wherein the candidate double edge is detected dependent upon the intensities of the selected pixel and two further pixels abutting the candidate double edge, predetermined gradients of at least the selected pixel and the two further pixels abutting the candidate edge; and a second detecting sub-step, of detecting a double edge detected by the first detecting sub-step that belongs to a thickening pixel, wherein a detected double edge that belongs to a thickening pixel is dependent upon a horizontal and vertical gradient of a diagonal pixel adjacent the selected pixel at the junction of the two edges of the detected double edge.
Claim 17
Dependent Claim
42 words
The method according to claim 15 , wherein one or more coefficient values of a portion of the convolution mask corresponding to each edge opposite to the detected double edge that belong to a thickening pixel are set to a predetermined value.
Claim 18
Dependent Claim
42 words
The method according to claim 1 , wherein said detecting step is carried out for each colour component of the selected pixel, and the one or more detected edges are dependent upon the largest intensity and gradient values of the colour components.
Claim 19
Dependent Claim
82 words
The method according to claim 1 , wherein said detecting step comprises the sub-step of: determining a candidate edge of the selected pixel as a detected edge if the intensities of the selected pixel and the further pixel are substantially different, the predetermined gradients of the selected and further pixels are both an absolute local maxima, and the predetermined gradients of the one or more diagonal pixels are not an absolute local maxima of the same sign as that of neighbouring pixels.
Claim 20
Dependent Claim
47 words
The method according to claim 18 , further comprising the steps of: comparing a modified value of the selected pixel with an original value of the selected pixel; restoring the selected pixel to its original value dependent upon a number of modified values of the digital image.
Claim 21
Dependent Claim
56 words
The method according to claim 18 , further comprising the steps of: determining the number of modified pixels in a predetermined neighbourhood of pixels containing the selected pixel; and if the number exceeds a threshold number of modified pixels, restoring one or more modified pixels in the neighbourhood to the original value of the respective pixel.
Claim 22
Dependent Claim
53 words
The method according to claim 18 , further comprising the steps of: determining if modified pixels in a predetermined neighbourhood of pixels containing the selected pixel conform to a predetermined pattern of pixels; and restoring any pixels determined not to conform to the predetermined pattern to the original value of the respective pixel.
Claim 23
Dependent Claim
78 words
The method according to claim 18 , further comprising the steps of: determining the number of modified pixels in a predetermined neighbourhood of pixels containing the selected pixel having increased values; determining the number of modified pixels in a predetermined neighbourhood of pixels containing the selected pixel having decreased values; and restoring the original value of the selected pixel if the number of increased-value modified pixels is not substantially the same as the number of decreased-value modified pixels.
Claim 24
Dependent Claim
55 words
The method according to claim 1 , wherein said detecting step comprises the sub-step of: determining a double edge if the intensities of the selected pixel and and two further pixels abutting the selected pixel are substantially different, and the predetermined gradients of the selected pixel and two further pixels are an absolute local maxima.
Claim 25
Dependent Claim
60 words
The method according to claim 23 , wherein said detecting step further comprises the sub-steps of: determining if the selected pixel is a thickening pixel; and setting to zero one or more coefficient values of a portion of said mask corresponding to an edge opposite to each edge of a said determined double edge associated with the determined thickening pixel.
Claim 26
Dependent Claim
49 words
The method according to claim 24 , wherein the selected pixel is determined to be a thickening pixel if the horizontal and vertical gradients of a pixel at the junction of the two edges of the determined double edge and diagonally abutting the selected pixel are absolute local minima.
Claim 27
Dependent Claim
46 words
The method according to claim 25 , further comprising the steps of: determining if pixels in a predetermined size neighbourhood of the selected pixel are also candidates for thickening; and if the neighbouring pixels are also thickening candidates, restoring the selected pixel to its original value.
Claim 28
Dependent Claim
48 words
The method according to claim 23 , further comprising the steps of: determining a zone containing the neighbourhood of pixels; and if the zone is an inverted zone having a dark background colour and a bright foreground colour, negating said predetermined gradients of the selected and neighbouring pixels.
Claim 29
Dependent Claim
46 words
The method according to claim 27 , wherein said step of determining a zone comprises the further steps of: choosing a representative window for the selected pixel; comparing local statistics regarding luminance of pixels in the representative window to obtain a zone; and smoothing the zone.
Claim 30
Independent Claim
143 words
An apparatus for smoothing jagged edges of oblique lines or curves in a digital image, said apparatus comprising: means for detecting one or more edges of a selected pixel in the digital image, wherein a candidate edge of the selected pixel for detection is detected dependent upon intensities of the selected pixel and a further pixel abutting the candidate edge of the selected pixel, predetermined gradients of at least the selected pixel and the further pixel, and predetermined gradients of one or more pixels diagonally adjacent the selected pixel; and means for modifying the selected pixel by applying a convolution mask to the selected pixel and a predetermined neighbourhood of pixels containing the selected pixel so as to smooth oblique edges without blurring horizontal or vertical edges, wherein coefficient values of the convolution mask are dependent upon the one or more detected edges.
Claim 31
Independent Claim
143 words
An apparatus for smoothing jagged edges of oblique lines or curves in a digital image, said apparatus comprising: means for detecting one or more edges of a selected pixel in the digital image, wherein a candidate edge of the selected pixel for detection is detected dependent upon intensities of the selected pixel and a further pixel abutting the candidate edge of the selected pixel, predetermined gradients of at least the selected pixel and the further pixel, and predetermined gradients of one or more pixels diagonally adjacent the selected pixel; and means for modifying the selected pixel by applying a convolution mask to the selected pixel and a predetermined neighbourhood of pixels containing the selected pixel so as to smooth oblique edges without blurring horizontal or vertical edges, wherein coefficient values of the convolution mask are dependent upon the one or more detected edges.
Claim 32
Dependent Claim
35 words
The apparatus according to claim 29 , wherein the detecting operation of said detection means is dependent upon a difference between the intensities of the selected pixel and the further pixel satisfying an intensity threshold.
Claim 33
Dependent Claim
28 words
The apparatus according to claim 30 , wherein the detecting operation of the detection means is dependent upon an absolute value of the difference exceeding said intensity threshold.
Claim 34
Dependent Claim
33 words
The apparatus according to claim 29 , wherein the detecting operation of said detection means is dependent upon the predetermined gradients of the selected pixel and the further pixel satisfying a gradient threshold.
Claim 35
Dependent Claim
35 words
The apparatus according to claim 32 , wherein the predetermined gradients of the selected pixel and the further pixel are either vertical or horizontal dependent upon the candidate edge being either horizontal or vertical, respectively.
Claim 36
Dependent Claim
25 words
The apparatus according to claim 32 , wherein the predetermined gradients of the selected pixel and the further pixel are greater than said gradient threshold.
Claim 37
Dependent Claim
25 words
The apparatus according to claim 32 , wherein the predetermined gradients of the selected pixel and the further pixel are less than said gradient threshold.
Claim 38
Dependent Claim
29 words
The apparatus according to claim 32 , wherein the detecting operation of said detection means is dependent upon the predetermined gradients of the diagonal pixels satisfying a gradient threshold.
Claim 39
Dependent Claim
39 words
The apparatus according to claim 36 , wherein: the predetermined gradients of the selected pixel and the further pixel are greater than said gradient threshold; and the predetermined gradients of the diagonal pixels are less than said gradient threshold.
Claim 40
Dependent Claim
39 words
The apparatus according to claim 36 , wherein: the predetermined gradients of the selected pixel and the further pixel are less than said gradient threshold; and the predetermined gradients of the diagonal pixels are greater than said gradient threshold.
Claim 41
Dependent Claim
38 words
The apparatus according to claim 29 , wherein if a single edge is detected, one or more coefficient values of a portion of said convolution mask next to the detected single edge are set to a predetermined value.
Claim 42
Dependent Claim
13 words
The apparatus according to claim 39 , wherein said predetermined value is zero.
Claim 43
Dependent Claim
38 words
The apparatus according to claim 29 , wherein if a double edge is detected, one or more coefficient values of each portion of said convolution mask next to the detected double edge are set to a predetermined value.
Claim 44
Dependent Claim
13 words
The apparatus according to claim 41 , wherein said predetermined value is zero.
Claim 45
Dependent Claim
125 words
The apparatus according to claim 34 or 35 , wherein the detection means comprises: a first detecting sub-module for detecting a double edge, wherein the candidate double edge is detected dependent upon the intensities of the selected pixel and two further pixels abutting the candidate double edge, predetermined gradients of at least the selected pixel and the two further pixels abutting the candidate edge; and a second detecting sub-module for detecting a double edge detected by the first detecting sub-module that belongs to a thickening pixel, wherein a detected double edge that belongs to a thickening pixel is dependent upon a horizontal and vertical gradient of a diagonal pixel adjacent the selected pixel at the junction of the two edges of the detected double edge.
Claim 46
Dependent Claim
42 words
The apparatus according to claim 43 , wherein one or more coefficient values of a portion of said convolution mask corresponding to each edge opposite to the detected double edge that belongs to a thickening pixel is set to a predetermined value.
Claim 47
Dependent Claim
46 words
The apparatus according to claim 29 , wherein the detecting operation of said detection means is carried out for each colour component of the selected pixel, and the one or more detected edges are dependent upon the largest intensity and gradient values of the colour components.
Claim 48
Dependent Claim
81 words
The apparatus according to claim 29 , wherein said detection means comprises: means for determining a candidate edge of the selected pixel as a detected edge if the intensities of the selected pixel and the further pixel are substantially different, the predetermined gradients of the selected and further pixels are both an absolute local maxima, and the predetermined gradients of the one or more diagonal pixels are not an absolute local maxima of the same sign as that of neighbouring pixels.
Claim 49
Dependent Claim
48 words
The apparatus according to claim 46 , further comprising: means for comparing a modified value of the selected pixel with the original value of the selected pixel; means for restoring the selected pixel to its original value dependent upon a number of modified values of the digital image.
Claim 50
Dependent Claim
57 words
The apparatus according to claim 46 , further comprising: means for determining the number of modified pixels in a predetermined neighbourhood of pixels containing the selected pixel; and means for, if the number exceeds a threshold number of modified pixels, restoring one or more modified pixels in the neighbourhood to the original value of the respective pixel.
Claim 51
Dependent Claim
54 words
The apparatus according to claim 46 , further comprising: means for determining if modified pixels in a predetermined neighbourhood of pixels containing the selected pixel conform to a predetermined pattern of pixels; and means for restoring any pixels determined not to conform to the predetermined pattern to the original value of the respective pixel.
Claim 52
Dependent Claim
81 words
The apparatus according to claim 46 , further comprising: means for determining the number of modified pixels in a predetermined neighbourhood of pixels containing the selected pixel having increased values; means for determining the number of modified pixels in a predetermined neighbourhood of pixels containing the selected pixel having decreased values; and means for restoring the original value of the selected pixel if the number of increased-value modified pixels is not substantially the same as the number of decreased-value modified pixels.
Claim 53
Dependent Claim
52 words
The apparatus according to claim 29 , wherein said detection means comprises: means for determining a double edge if the intensities of the selected pixel and two further pixels abutting the selected pixel are substantially different, and the predetermined gradients of the selected pixel and two further pixels are absolute local maxima.
Claim 54
Dependent Claim
61 words
The apparatus according to claim 51 , wherein said detection means further comprises: means for determining if the selected pixel is a thickening pixel; and means for setting to zero one or more coefficient values of a portion of said mask corresponding to an edge opposite to each edge of a said determined double edge associated with the determined thickening pixel.
Claim 55
Dependent Claim
57 words
The apparatus according to claim 52 , wherein said selected pixel is determined to be a thickening pixel if the selected pixel has two edges and if the horizontal and vertical gradients of a pixel at the junction of the two edges of the determined double edge and diagonally abutting the selected pixel are absolute local minima.
Claim 56
Dependent Claim
47 words
The apparatus according to claim 53 , further comprising: means for determining if pixels in a predetermined size neighbourhood of the selected pixel are also candidates for thickening; and means for, if the neighbouring pixels are also thickening candidates, restoring the selected pixel to its original value.
Claim 57
Dependent Claim
49 words
The apparatus according to claim 51 , further comprising: means for determining a zone containing the neighbourhood of pixels; and means for, if the zone is an inverted zone having a dark background colour and a bright foreground colour, negating the predetermined gradients of the selected and neighbouring pixels.
Claim 58
Dependent Claim
48 words
The apparatus according to claim 55 , wherein said means for determining a zone comprises: means for choosing a representative window for the selected pixel; means for comparing local statistics regarding luminance of pixels in the representative window to obtain a zone; and means for smoothing the zone.
Claim 59
Dependent Claim
158 words
A computer program product including a computer readable medium having recorded thereon a computer program for smoothing jagged edges of oblique lines or curves in a digital image, said computer program product comprising: means for detecting one or more edges of a selected pixel in the digital image, wherein a candidate edge of the selected pixel for detection is detected dependent upon intensities of the selected pixel and a further pixel abutting the candidate edge of the selected pixel, predetermined gradients of at least the selected pixel and the further pixel, and predetermined gradients of one or more pixels diagonally adjacent the selected pixel; and means for modifying the selected pixel by applying a convolution mask to the selected pixel and a predetermined neighbourhood of pixels containing the selected pixel so as to smooth oblique edges without blurring horizontal or vertical edges, wherein coefficient values of the convolution mask are dependent upon the one or more detected edges.
Claim 60
Dependent Claim
158 words
A computer program product including a computer readable medium having recorded thereon a computer program for smoothing jagged edges of oblique lines or curves in a digital image, said computer program product comprising: means for detecting one or more edges of a selected pixel in the digital image, wherein a candidate edge of the selected pixel for detection is detected dependent upon intensities of the selected pixel and a further pixel abutting the candidate edge of the selected pixel, predetermined gradients of at least the selected pixel and the further pixel, and predetermined gradients of one or more pixels diagonally adjacent the selected pixel; and means for modifying the selected pixel by applying a convolution mask to the selected pixel and a predetermined neighbourhood of pixels containing the selected pixel so as to smooth oblique edges without blurring horizontal or vertical edges, wherein coefficient values of the convolution mask are dependent upon the one or more detected edges.
Claim 61
Dependent Claim
37 words
The computer program product according to claim 57 , wherein the detecting operation of the detection means is dependent upon a difference between the intensities of the selected pixel and the further pixel satisfying an intensity threshold.
Claim 62
Dependent Claim
30 words
The computer program product according to claim 58 , wherein the detecting operation of the detection means is dependent upon an absolute value of the difference exceeding said intensity threshold.
Claim 63
Dependent Claim
35 words
The computer program product according to claim 57 , wherein the detecting operation of the detection means is dependent upon the predetermined gradients of the selected pixel and the further pixel satisfying a gradient threshold.
Claim 64
Dependent Claim
37 words
The computer program product according to claim 60 , wherein the predetermined gradients of the selected pixel and the further pixel are either vertical or horizontal dependent upon the candidate edge being either horizontal or vertical, respectively.
Claim 65
Dependent Claim
27 words
The computer program product according to claim 60 , wherein the predetermined gradients of the selected pixel and the further pixel are greater than said gradient threshold.
Claim 66
Dependent Claim
27 words
The computer program product according to claim 60 , wherein the predetermined gradients of the selected pixel and the further pixel are less than said gradient threshold.
Claim 67
Dependent Claim
31 words
The computer program product according to claim 60 , wherein the detecting operation of the detection means is dependent upon the predetermined gradients of the diagonal pixels satisfying a gradient threshold.
Claim 68
Dependent Claim
41 words
The computer program product according to claim 64 , wherein: the predetermined gradients of the selected pixel and the further pixel are greater than said gradient threshold; and the predetermined gradients of the diagonal pixels are less than said gradient threshold.
Claim 69
Dependent Claim
41 words
The computer program product according to claim 64 , wherein: the predetermined gradients of the selected pixel and the further pixel are less than said gradient threshold; and the predetermined gradients of the diagonal pixels are greater than said gradient threshold.
Claim 70
Dependent Claim
38 words
The computer program product according to claim 57 , wherein if a single edge is detected, one or more coefficient values of a portion of said next to the detected single edge are set to a predetermined value.
Claim 71
Dependent Claim
15 words
The computer program product according to clam 67 , wherein said predetermined value is zero.
Claim 72
Dependent Claim
15 words
The computer program product according to clam 67 , wherein said predetermined value is zero.
Claim 73
Dependent Claim
40 words
The computer program product according to claim 57 , wherein if a double edge is detected, one or more coefficient values of each portion of said convolution mask next to the detected double edge are set to a predetermined value.
Claim 74
Dependent Claim
15 words
The computer program product according to claim 69 , wherein said predetermined value is zero.
Claim 75
Dependent Claim
127 words
The computer program product according to claim 62 or 63 , wherein the detection means comprises: a first detecting sub-module for detecting a double edge, wherein the candidate double edge is detected dependent upon the intensities of the selected pixel and two further pixels abutting the candidate double edge, predetermined gradients of at least the selected pixel and the two further pixels abutting the candidate edge; and a second detecting sub-module for detecting a double edge detected by the first detecting sub-module that belongs to a thickening pixel, wherein a detected double edge that belongs to a thickening pixel is dependent upon a horizontal and vertical gradient of a diagonal pixel adjacent the selected pixel at the junction of the two edges of the detected double edge.
Claim 76
Dependent Claim
44 words
The computer program product according to claim 71 , wherein one or more coefficient values of a portion of said convolution mask corresponding to each edge opposite to the detected double edge that belongs to a thickening pixel are set to a predetermined value.
Claim 77
Dependent Claim
48 words
The computer program product according to claim 57 , wherein the detecting operation of said detection means is carried out for each colour component of the selected pixel, and the one or more detected edges are dependent upon the largest intensity and gradient values of the colour components.
Claim 78
Dependent Claim
82 words
The computer program product according to claim 57 , wherein said detection means comprises: means for determining a candidate edge of the selected pixel as a detected edge if the intensities of the selected pixel and the further are substantially different, the predetermined gradients of the selected and further pixels are both an absolute local maxima, and the predetermined gradients of the one or more diagonal pixels are not an absolute local maxima of the same sign as that of neighbouring pixels.
Claim 79
Dependent Claim
50 words
The computer program product according to claim 74 , further comprising: means for comparing a modified value of the selected pixel with the original value of the selected pixel; means for restoring the selected pixel to its original value dependent upon a number of modified values of the digital image.
Claim 80
Dependent Claim
59 words
The computer program product according to claim 74 , further comprising: means for determining the number of modified pixels in a predetermined neighbourhood of pixels containing the selected pixel; and means for, if said number exceeds a threshold number of modified pixels, restoring one or more modified pixels in said neighbourhood to the original value of the respective pixel.
Claim 81
Dependent Claim
56 words
The computer program product according to claim 74 , further comprising: means for determining if modified pixels in a predetermined neighbourhood of pixels containing the selected pixel conform to a predetermined pattern of pixels; and means for restoring any pixels determined not to conform to the predetermined pattern to the original value of the respective pixel.
Claim 82
Dependent Claim
83 words
The computer program product according to claim 74 , further comprising: means for determining the number of modified pixels in a predetermined neighbourhood of pixels containing the selected pixel having increased values; means for determining the number of modified pixels in a predetermined neighbourhood of pixels containing the selected pixel having decreased values; and means for restoring the original value of the selected pixel if the number of increased-value modified pixels is not substantially the same as the number of decreased-value modified pixels.
Claim 83
Dependent Claim
55 words
The computer program product according to claim 57 , wherein said detection means comprises: means for determining a double edge if the intensities of the selected pixel and and two further pixels abutting the selected pixel are substantially different, and the predetermined gradients of the selected pixel and two further pixels are absolute local maxima.
Claim 84
Dependent Claim
63 words
The computer program product according to claim 79 , wherein said detection means further comprises: means for determining if the selected pixel is a thickening pixel; and means for setting to zero one or more coefficient values of a portion of said mask corresponding to an edge opposite to each edge of a said determined double edge associated with the determined thickening pixel.
Claim 85
Dependent Claim
59 words
The computer program product according to claim 80 , wherein the selected pixel is determined to be a thickening pixel if the selected pixel has two edges and if the horizontal and vertical gradients of a pixel at the junction of the two edges of the determined double edge and diagonally abutting the selected pixel are absolute local minima.
Claim 86
Dependent Claim
49 words
The computer program product according to claim 81 , further comprising: means for determining if pixels in a predetermined size neighbourhood of the selected pixel are also candidates for thickening; and means for, if the neighbouring pixels are also thickening candidates, restoring the selected pixel to its original value.
Claim 87
Dependent Claim
51 words
The computer program product according to claim 79 , further comprising: means for determining a zone containing the neighbourhood of pixels; and means for, if the zone is an inverted zone having a dark background colour and a bright foreground colour, negating said predetermined gradients of the selected and neighbouring pixels.
Claim 88
Dependent Claim
50 words
The computer program product according to claim 83 , wherein said means for determining a zone comprises: means for choosing a representative window for the selected pixel; means for comparing local statistics regarding luminance of pixels in the representative window to obtain a zone; and means for smoothing the zone.
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