US5818978A
Expired / Lapsed
US
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Image pre-processor for character image recognition system
Assignee: Canon Inc
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Filing: 1997-01-27
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Granted: 1998-10-06
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Expires: 2017-01-27
Abstract
Abstract A personal imaging computer system, which is connectable to and operable with a computerized local or wide area network, identifies characters in a document on which the characters are formed. The system scans the document to obtain a gray-scale image of the document, de-skews the gray-scale image, generates a binary image from the de-skewed gray-scale image by comparing the gray-scale image with the threshold, segments the binary image to locate individual characters within the binary image and to determine the shape of the individual characters, extracts gray-scale image information from the gray-scale image for each such individual character based on the location and shape of the character in the binary image, recognition-processes the extracted gray scale image information to determine the identity of the character, and stores the identity of the character. Image pre-processing for the personal imaging computer system includes pre-processing for de-skewing the image, for obtaining and applying a global threshold which converts a gray-scale image to a binary image, for removing underlines from underlined characters in the image, for obtaining connected components within a binary image, and for applying plural sets of rules to the connected components so as to filter text-type connected components from non-text type connected components, whereby only text-type connected components are subjected to character recognition processing.
Inventors
- 👤 Hussein Al-Hussein
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 09:09
CPC Classifications
G; G06; G06V; G06V30/00; G06V30/40; G06V30/41; G06V30/413; G06V30/10; G06V30/14; G06V30/146; G06V30/1475; G06V30/1478; G06V30/148; G06V30/155; G06V30/16; G06V30/162
Claims Analysis
Total Claims: 44
Claim 1
Independent Claim
124 words
An image processing apparatus for de-skewing an image of a document, the image comprised by pixels arranged into rows and columns, said apparatus comprising: measuring means for measuring skew angle of the image; rotation-transforming means for rotation-transforming pixels of the image by a mathematical rotation transformation so as to reduce the skew angle to approximately zero; pixel-shifting means for pixel-shifting columns of the image so as to reduce the skew angle to approximately zero; and determination means for causing said rotation-transforming means to reduce skew angle in a case where the measured skew angle is greater than a predetermined limit, and for causing said pixel-shifting means to reduce skew angle in a case where the measured skew angle is less than the predetermined limit.
Claim 2
Dependent Claim
124 words
An image processing apparatus for de-skewing an image of a document, the image comprised by pixels arranged into rows and columns, said apparatus comprising: measuring means for measuring skew angle of the image; rotation-transforming means for rotation-transforming pixels of the image by a mathematical rotation transformation so as to reduce the skew angle to approximately zero; pixel-shifting means for pixel-shifting columns of the image so as to reduce the skew angle to approximately zero; and determination means for causing said rotation-transforming means to reduce skew angle in a case where the measured skew angle is greater than a predetermined limit, and for causing said pixel-shifting means to reduce skew angle in a case where the measured skew angle is less than the predetermined limit.
Claim 3
Dependent Claim
44 words
An image processing apparatus according to claim 1, wherein said measuring means performs a rough measurement to obtain a rough determination of skew angle, and a fine measurement to obtain a fine measure of skew angle in a neighborhood around the rough skew angle.
Claim 4
Dependent Claim
46 words
An image processing apparatus according to claim 1, wherein said measuring means sub-samples the image, binarizes the image, performs rough Hough transformation to obtain a rough skew angle and performs fine Hough transformation in a neighborhood around the rough skew angle to determine the skew angle.
Claim 5
Dependent Claim
18 words
An image processing apparatus according to claim 1, wherein said measuring means omits measuring skew angle of pictures.
Claim 6
Dependent Claim
17 words
An image processing apparatus according to claim 1, wherein said rotation-transforming means is comprised by matrix multiplication.
Claim 7
Dependent Claim
27 words
An image processing apparatus according to claim 1, wherein in said pixel shifting means pixel-shifts columns of the image in blank areas between characters in the image.
Claim 8
Dependent Claim
38 words
An image processing apparatus according to claim 6, wherein said pixel shifting means includes determining means for determining a vertical shift factor, and wherein the vertical shift factor is accumulated until a blank area between characters is reached.
Claim 9
Dependent Claim
32 words
An image processing apparatus according to claim 1, wherein said pixel shifting means includes determining means for determining a vertical shift factor by which all columns of the image are successively shifted.
Claim 10
Dependent Claim
138 words
An image processing apparatus for de-skewing an image of a document, the image comprised by pixels arranged into rows and columns, said apparatus comprising: a memory for storing the image and for storing instruction sequences by which the image is processed; and a processor for executing the stored instruction sequences; wherein the stored instruction sequences include process steps adapted to cause said processor to (a) measure skew angle of the image, (b) rotation-transform pixels of the image by applying a mathematical rotation transformation so as to reduce the skew angle to approximately zero in a case where the measured skew angle is greater than a predetermined limit, and (c) pixel-shift columns of the image so as to reduce the skew angle to approximately zero in a case where the measured skew angle is less than the predetermined limit.
Claim 11
Dependent Claim
138 words
An image processing apparatus for de-skewing an image of a document, the image comprised by pixels arranged into rows and columns, said apparatus comprising: a memory for storing the image and for storing instruction sequences by which the image is processed; and a processor for executing the stored instruction sequences; wherein the stored instruction sequences include process steps adapted to cause said processor to (a) measure skew angle of the image, (b) rotation-transform pixels of the image by applying a mathematical rotation transformation so as to reduce the skew angle to approximately zero in a case where the measured skew angle is greater than a predetermined limit, and (c) pixel-shift columns of the image so as to reduce the skew angle to approximately zero in a case where the measured skew angle is less than the predetermined limit.
Claim 12
Dependent Claim
52 words
An apparatus according to claim 9, wherein said stored instruction sequences include process steps adapted to cause said processor to perform a rough measurement to obtain a rough determination of skew angle, and a fine measurement to obtain a fine measure of skew angle in a neighborhood around the rough skew angle.
Claim 13
Dependent Claim
54 words
An apparatus according to claim 9, wherein said stored instruction sequences include process steps adapted to cause said processor to sub-sample the image, binarize the image, perform rough Hough transformation to obtain a rough skew angle and perform fine Hough transformation in a neighborhood around the rough skew angle to determine the skew angle.
Claim 14
Dependent Claim
27 words
An apparatus according to claim 9, wherein said stored instruction sequences include process steps adapted to cause said processor to omit measurement of skew angle of pictures.
Claim 15
Dependent Claim
14 words
An apparatus according to claim 9, wherein said rotation-transform is comprised by matrix multiplication.
Claim 16
Dependent Claim
33 words
An apparatus according to claim 9, wherein said stored instruction sequences include process steps adapted to cause said processor to pixel-shift columns of the image in blank areas between characters in the image.
Claim 17
Dependent Claim
41 words
An apparatus according to claim 14, wherein said stored instruction sequences include process steps adapted to cause said processor to determine a vertical shift factor, and wherein the vertical shift factor is accumulated until a blank area between characters is reached.
Claim 18
Dependent Claim
35 words
An apparatus according to claim 9, wherein said stored instruction sequences include process steps adapted to cause said processor to determine a vertical shift factor by which all columns of the image are successively shifted.
Claim 19
Dependent Claim
95 words
An image processing method for de-skewing an image of a document, the image comprised by pixels arranged into rows and columns, said method comprising the steps of: measuring skew angle of the image; rotation-transforming pixels of the image by applying a mathematical rotation transformation so as to reduce the skew angle to approximately zero in a case where the measured skew angle is greater than a predetermined limit; and pixel-shifting columns of the image so as to reduce the skew angle in a case where the measured skew angle is less than the predetermined limit.
Claim 20
Dependent Claim
95 words
An image processing method for de-skewing an image of a document, the image comprised by pixels arranged into rows and columns, said method comprising the steps of: measuring skew angle of the image; rotation-transforming pixels of the image by applying a mathematical rotation transformation so as to reduce the skew angle to approximately zero in a case where the measured skew angle is greater than a predetermined limit; and pixel-shifting columns of the image so as to reduce the skew angle in a case where the measured skew angle is less than the predetermined limit.
Claim 21
Dependent Claim
44 words
A method according to claim 17, wherein said measuring step includes a rough measuring step for obtaining a rough determination of skew angle, and a fine measuring step for obtaining a fine measure of skew angle in a neighborhood around the rough skew angle.
Claim 22
Dependent Claim
48 words
A method according to claim 17, wherein said measuring step includes the steps of sub-sampling the image, binarizing the image, performing rough Hough transformation to obtain a rough skew angle and performing fine Hough transformation in a neighborhood around the rough skew angle to determine the skew angle.
Claim 23
Dependent Claim
16 words
A method according to claim 17, wherein said measuring step omits measuring skew angle of pictures.
Claim 24
Dependent Claim
15 words
A method according to claim 17, wherein said rotation-transforming step is comprised by matrix multiplication.
Claim 25
Dependent Claim
26 words
A method according to claim 17, wherein in said pixel shifting step, columns of the image are pixel-shifted in blank areas between characters in the image.
Claim 26
Dependent Claim
36 words
A method according to claim 22, wherein said pixel shifting step includes a step of determining a vertical shift factor, and wherein the vertical shift factor is accumulated until a blank area between characters is reached.
Claim 27
Dependent Claim
30 words
A method according to claim 17, wherein said pixel shifting step includes the step of determining a vertical shift factor by which all columns of the image are successively shifted.
Claim 28
Dependent Claim
130 words
Computer-executable process steps stored on a computer readable medium, the computer-executable process steps to de-skew an image of a document which contains character, the image comprised by pixels arranged into rows and columns, said process steps including: a measuring step to measure skew angle of the image; a comparing step to compare the skew angle to a predetermined limit; a rotation step to rotation-transform pixels of the image by applying a mathematical rotation transformation so as to reduce the skew angle to approximately zero in a case where the skew angle is greater than the predetermined limit; and a shifting step to pixel-shift columns of the image so as to reduce the skew angle to approximately zero in a case where the skew angle is less than a predetermined limit.
Claim 29
Dependent Claim
130 words
Computer-executable process steps stored on a computer readable medium, the computer-executable process steps to de-skew an image of a document which contains character, the image comprised by pixels arranged into rows and columns, said process steps including: a measuring step to measure skew angle of the image; a comparing step to compare the skew angle to a predetermined limit; a rotation step to rotation-transform pixels of the image by applying a mathematical rotation transformation so as to reduce the skew angle to approximately zero in a case where the skew angle is greater than the predetermined limit; and a shifting step to pixel-shift columns of the image so as to reduce the skew angle to approximately zero in a case where the skew angle is less than a predetermined limit.
Claim 30
Dependent Claim
45 words
Computer-executable process steps according to claim 25, wherein said measuring step includes a rough measuring step which obtains a rough determination of skew angle, and a fine measuring step which obtains a fine measure of skew angle in a neighborhood around the rough skew angle.
Claim 31
Dependent Claim
64 words
Computer-executable process steps according to claim 25, wherein said measuring step includes a sub-sampling step which sub-samples the image, a binarizing step which binarizes the image, a first performing step which performs rough Hough transformation to obtain a rough skew angle and a second performing step which performs fine Hough transformation in a neighborhood around the rough skew angle to determine the skew angle.
Claim 32
Dependent Claim
17 words
Computer-executable process steps according to claim 25, wherein said measuring step omits measuring skew angle of pictures.
Claim 33
Dependent Claim
16 words
Computer-executable process steps according to claim 25, wherein said rotation-transforming step is comprised by matrix multiplication.
Claim 34
Dependent Claim
27 words
Computer-executable process steps according to claim 25, wherein in said pixel shifting step, columns of the image are pixel-shifted in blank areas between characters in the image.
Claim 35
Dependent Claim
38 words
Computer-executable process steps according to claim 30, wherein said pixel shifting step includes a determining step which determines a vertical shift factor, and wherein the vertical shift factor is accumulated until a blank area between characters is reached.
Claim 36
Dependent Claim
32 words
Computer-executable process steps according to claim 25, wherein said pixel shifting step includes a determining step which determines a vertical shift factor by which all columns of the image are successively shifted.
Claim 37
Dependent Claim
33 words
An image processing apparatus according to claim 1, wherein the mathematical transformation is such that each pixel in the reduced skew image is a mathematical combination of several pixels in the skewed image.
Claim 38
Dependent Claim
35 words
An image process apparatus according to claim 1 or 33, wherein pixel-shifting is such that each pixel in the reduced skew image has a value found identically in a single pixel of the skewed image.
Claim 39
Dependent Claim
33 words
An image processing apparatus according to claim 9, wherein the mathematical transformation is such that each pixel in the reduced skew image is a mathematical combination of several pixels in the skewed image.
Claim 40
Dependent Claim
35 words
An image process apparatus according to claim 9 or 35, wherein pixel-shifting is such that each pixel in the reduced skew image has a value found identically in a single pixel of the skewed image.
Claim 41
Dependent Claim
33 words
An image processing method according to claim 17, wherein the mathematical transformation is such that each pixel in the reduced skew image is a mathematical combination of several pixels in the skewed image.
Claim 42
Dependent Claim
35 words
An image process method according to claim 17 or 37, wherein pixel-shifting is such that each pixel in the reduced skew image has a value found identically in a single pixel of the skewed image.
Claim 43
Dependent Claim
32 words
Computer-executable process steps according to claim 25, wherein the mathematical transformation is such that each pixel in the reduced skew image is a mathematical combination of several pixels in the skewed image.
Claim 44
Dependent Claim
34 words
Computer-executable process steps according to claim 25 or 39, wherein pixel-shifting is such that each pixel in the reduced skew image has a value found identically in a single pixel of the skewed image.
References Cited (Backward Citations)
US4802229A
Cited
US4558461A
Cited
EP0176910A1
Cited
EP0177823A1
Cited
US4723297A
Cited
US4748678A
Cited
US4985930A
Cited
US5101448A
Cited
JPH02214976A
Cited
US5050225A
Cited
US5181260A
Cited
EP0431962A2
Cited
US5187753A
Cited
US5245676A
Cited
US5054098A
Cited
US5452374A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2001-10-05 | 2002-04-06 | 2002-10-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-10-05 | 2006-04-06 | 2006-10-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-10-05 | 2010-04-06 | 2010-10-06 | $7700.00 | Window Closed / Lapsed |