Global localization by fast image matching
First Claim
1. A method of determining a portion of a document corresponding to a captured image, comprising:
- obtaining a captured image of a portion of a document, the document having a pattern that uniquely identifies different positions in the document;
determining obscured areas of the document in which the pattern is at least partially obscured;
designating a reference pixel in the captured image;
identifying locations in the obscured areas of the document that may correspond with the reference pixel;
comparing the captured image with different portions of the document, such that the reference pixel is compared with one or more of the identified locations; and
based upon the comparison, determining an identified location in the document that corresponds with the reference pixel,wherein determining an identified location in the document that corresponds with the reference pixel further includeswarping the captured image so that the scale and rotation of the captured image match the scale and rotation of the document;
rotating the warped captured image at multiples of 90°
; and
determining a correlation value for each comparison of the image with a portion of a document.
2 Assignments
0 Petitions
Accused Products
Abstract
An efficient technique is provided for determining a portion of a document corresponding to a captured image. Areas of a document in which the pattern is at least partially obscured are identified. A reference pixel in the image is selected, and an offset between the pixel and the pattern is determined. A pixel-by-pixel comparison is then made of the image with the document such that the reference pixel is only compared with locations in the document that are both within the identified areas and have the determined offset from the pattern. The comparison with the highest correspondence between the image pixels and the electronic document then identifies the position of the reference pixel relative to the electronic document.
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Citations
21 Claims
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1. A method of determining a portion of a document corresponding to a captured image, comprising:
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obtaining a captured image of a portion of a document, the document having a pattern that uniquely identifies different positions in the document; determining obscured areas of the document in which the pattern is at least partially obscured; designating a reference pixel in the captured image; identifying locations in the obscured areas of the document that may correspond with the reference pixel; comparing the captured image with different portions of the document, such that the reference pixel is compared with one or more of the identified locations; and based upon the comparison, determining an identified location in the document that corresponds with the reference pixel, wherein determining an identified location in the document that corresponds with the reference pixel further includes warping the captured image so that the scale and rotation of the captured image match the scale and rotation of the document; rotating the warped captured image at multiples of 90°
; anddetermining a correlation value for each comparison of the image with a portion of a document. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A computer-readable medium storing a program which when executed causes a computer to perform:
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receiving a captured image of a portion of a document, wherein the document has a pattern that uniquely identifies different positions in the document and wherein the portion of the pattern in the captured image is at least partially obscured; determining obscured areas of the document in which the pattern is at least partially obscured; determining a spatial relationship between a reference pixel in the captured image and the pattern within the captured image; identifying locations in the obscured areas of the document exhibiting a similar spatial relationship to the pattern in the obscured areas; warping the captured image so that the scale and orientation of the captured image matches the scale and orientation of the document; rotating the warped captured image at multiples of 90°
;comparing the captured image with determined obscured areas of the document by comparing the captured image with portions of the obscured areas of the document associated with the identified locations; determining a correlation value for each comparison of the image with a portion of a document; and identifying the position of the portion of the document corresponding to the captured image. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method for determining a portion of a document corresponding to a captured image, comprising:
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receiving a captured image of a portion of a document, wherein the document has a randomly- or pseudorandomly-generated pattern that uniquely identifies different positions in the document and wherein the portion of the pattern in the captured image is at least partially obscured; warping the captured image so that the scale and orientation of the captured image matches the scale and orientation of the document; determining obscured areas of the document by determining, for each of given pixels of the document, whether the amount of the pattern that is obscured in a portion of the document around each given pixel is sufficient to preclude unique identification of the position of the portion within the document; determining a pixel offset between a reference pixel in the captured image and the pattern within the captured image, wherein the pixel offset represents the shortest distance between the reference pixel and an unobscured portion of the pattern; identifying locations in the obscured areas of the document with a comparable pixel offset; comparing the captured image with portions of the obscured areas of the document associated with the identified locations, repeating the comparison for each 90°
rotation of the captured image;identifying the position of the portion of the document corresponding to the captured image as the position of the portion of the document associated with the comparison which produces a correlation at least 10% higher than the other comparisons.
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Specification