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EP0485051A2
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Detecting skew in digitised images
Assignee: Fujitsu Services Ltd
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Filing: 1991-07-11
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Granted: —
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Expires: 2011-07-11
Abstract
Abstract A method of detecting skew in a digitised document image as described. The method comprises forming a transformation of the image, to generate an array H(D, A) representing the number of black pixels which lie on lines with angle A and perpendicular displacement D. The dominant angle A in this array, determined by calculating an energy function from the array, is taken as the angle of skew.
Inventors
- 👤 Gary Stuart Donald Farrow
- 👤 Costos Spyros Xydeas
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 13:29
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/00681; G; G06; G06V; G06V30/00; G06V30/10; G06V30/14; G06V30/146; G06V30/1475; G06V30/1478; H04N1/00684; H04N1/00718; H04N1/00763; H04N1/00766; H04N1/00785; H04N1/00787
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
86 words
A method of detecting skew in a digitised document image, comprising the steps: a) performing a transformation on the image to generate an array H(D, A) where each element H(D, A) in the array represents the number of pixels of a predetermined characteristic (e.g. black pixels) in the image that lie on a straight line at an angle A to a predetermined direction and at a perpendicular distance D from a predetermined origin, and b) finding a dominant value of the angle A in the array
Claim 2
Dependent Claim
56 words
A method according to Claim 1 wherein the step of finding the dominant value of the angle comprises the steps: a) for each value of A, generating a function e(A) equal to the sum of the squares of all elements H(D, A) corresponding to that value of A, and b) finding the maximum value of e(A).
Claim 3
Dependent Claim
22 words
A method according to Claim 1 or 2 including the step of coarsening the digitised document image prior to performing said transformation.
Claim 4
Independent Claim
24 words
A method according to any preceding claim, including the further step of re-aligning said image by a correction angle equal to said dominant value.
Claim 5
Dependent Claim
104 words
Document processing apparatus comprising: a) means (31) for scanning and digitising a document to produce a digitised document image, b) means (33) for performing a translation on the image to generate an array H(D, A) where each element H(D, A) in the array represents the number of pixels of a predetermined characteristic (e.g. black pixels) in the image that lie on a straight line at an angle A to a predetermined direction and at a perpendicular distance D from a predetermined origin, and c) means (34) for processing the array H(D, A) to find a dominant value of the angle A in the array.
Claim 6
Dependent Claim
53 words
Apparatus according to Claim 5 wherein said means (34) for processing the array comprises: a) means for generating, for each value of A, a function e(A) equal to the sum of squares of all elements H(D, A) corresponding to that value of A, and b) means for finding the maximum value of e(A).
Claim 7
Dependent Claim
22 words
Apparatus according to Claim 5 or 6 further including means (32) for coarsening the digitised document image prior to performing said transformation.
Claim 8
Dependent Claim
31 words
Apparatus according to any one of Claims 5 to 7 further including means (35) for re-aligning said document by a correction angle equal to said dominant value of the angle A.
References Cited (Backward Citations)
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