METHOD FOR MARKING GRAPHICAL ELEMENTS AND METHOD FOR DETECTING SAID MARKING IN A GRAPHICAL ELEMENT
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Abstract
Method for marking graphical elements comprising the steps of selecting at least three coherent edge portions (6) of a graphical element (1), wherein the relative orientation of the coherent edge portions (6) is constant and/or smoothly varies along their entire length, the coherent edge portions (6) comprising at least two reference edge portions (66) and one edge portion to mark (67); defining a family of smooth and non-intersecting curves (65), said curves (65) intersecting all of the coherent edge portions (66, 67); shifting the edge portion to mark (67) along the curves (65) relative to the reference edge portions (66); and method for detecting a marking in a graphical element, comprising the steps of locating an encoding area (7) in a digital image of a graphical element (1); retrieving at least two reference edge portions (66) and at least one modified edge portion (68) of the encoding area (7) in the digital image; and determining the relative position of the modified edge portion (68) relative to the reference edge portions (66).
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Citations
26 Claims
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1-15. -15. (canceled)
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16. A method for marking graphical elements comprising the steps of:
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estimating axes of alignment of characters and symbols in said graphical element; defining zones of high visibility around these axes of alignment; defining at least one zone of low visibility comprising parts of said graphical element that are not comprised in any of said zones of high visibility; selecting at least three coherent edge portions of said graphical element in said at least one zone of low visibility, such that the relative orientation of said coherent edge portions is constant and/or smoothly varies along their entire length, said at least three coherent edge portions comprising at least two reference edge portions and one edge portion to mark located between said at least two reference edge portions; defining a family of smooth and non-intersecting curves, said curves intersecting all of said at least three coherent edge portions; defining an encoding area comprising said at least three coherent edge portions and said curves, said encoding area being limited on two opposite sides by said at least two reference edges portions and on two other opposite sides by curves of said family of curves; shifting said edge portion to mark along said curves relative to said at least two reference edge portions; and storing information about said at least one encoding area in a descriptor of said graphical element. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 26)
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Specification