ROBUST INTEREST POINT DETECTOR AND DESCRIPTOR
First Claim
1. A method for deriving a descriptor of an interest point in an image having a plurality of pixels, the interest point having a location in the image and an orientation, the method comprising:
- identifying a neighbourhood around the interest point aligned with the orientation of the interest point, the neighbourhood comprising a set of pixels;
inspecting contrasts in the neighbourhood of the interest point in at least one direction having a fixed relation to the orientation using at least one digital filter to thereby generate first scalar contrast measures for each direction independently, andgenerating a multidimensional descriptor comprising first elements, each first element being a second scalar contrast measure that is a combination of the first scalar contrast measures from only one direction.
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Accused Products
Abstract
Methods and apparatus for operating on images are described, in particular methods and apparatus for interest point detection and/or description working under different scales and with different rotations, e.g. for scale-invariant and rotation-invariant interest point detection and/or description. The present invention can provide improved or alternative apparatus and methods for matching interest points either in the same image or in a different image. The present invention can provide alternative or improved software for implementing any of the methods of the invention. The present invention can provide alternative or improved data structures created by multiple filtering operations to generate a plurality of filtered images as well as data structures for storing the filtered images themselves, e.g. as stored in memory or transmitted through a network. The present invention can provide alternative or improved data structures including descriptors of interest points in images, e.g. as stored in memory or transmitted through a network as well as datastructures associating such descriptors with an original copy of the image or an image derived therefrom, e.g. a thumbnail image.
110 Citations
32 Claims
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1. A method for deriving a descriptor of an interest point in an image having a plurality of pixels, the interest point having a location in the image and an orientation, the method comprising:
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identifying a neighbourhood around the interest point aligned with the orientation of the interest point, the neighbourhood comprising a set of pixels; inspecting contrasts in the neighbourhood of the interest point in at least one direction having a fixed relation to the orientation using at least one digital filter to thereby generate first scalar contrast measures for each direction independently, and generating a multidimensional descriptor comprising first elements, each first element being a second scalar contrast measure that is a combination of the first scalar contrast measures from only one direction. - View Dependent Claims (3, 4, 5, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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2. A method for deriving a descriptor of an interest point in an image having a plurality of pixels, the interest point having a location in the image and an orientation, the method comprising:
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identifying a region in a neighbourhood around the interest point aligned with the orientation of the interest point, the neighbourhood comprising a set of pixels; examining tiles of the region, and for each tile generating a contrast related response using at least one digital filter, summing response values from application of the at least one digital filter in at least two orthogonal directions to generate summed values, and generating a multidimensional descriptor having first elements, each first element being based on the summed values.
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6. A method for deriving a descriptor of an interest point in an image having a plurality of pixels, the interest point having a location in the image and an orientation, and a neighbourhood having been defined around the interest point aligned with the orientation of the interest point, the neighbourhood comprising a set of pixels;
- the method comprising;
inspecting contrasts in the neighbourhood of the interest point using at least one digital filter, generating a multidimensional descriptor based on the results of the application of the at least one digital filter and absolute values of these results. - View Dependent Claims (7)
- the method comprising;
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8. A method for assigning the orientation of an interest point in an image having a plurality of pixels, the interest point having a location, the method comprising:
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identifying a region enclosing the interest point, determining an orientation for the interest point by; examining a plurality of tiles of the region, each tile comprising a plurality of pixels, determining for each tile filtered values related to contrast in two directions to thereby determine for that tile an orientation and a magnitude for that orientation, and assigning an orientation to the interest point by selecting the determined orientation with largest magnitude.
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21. A method for determining an interest point in an image having a plurality of pixels suitable for working at different scales and/or rotations, the method comprising:
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filtering the image using at least one digital filter, and selecting an interest point based on determining a measure resulting from application of the at least one digital filter, the measure being a non-linear combination of the outputs of the at least one digital filter, the measure capturing variations of an image parameter in more than one dimension or direction, the at least one digital filter being a combination of box filters, at least one box filter having a spatial extent greater than one pixel. - View Dependent Claims (22, 25, 26, 27, 28, 29, 30, 31, 32)
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23. A method for determining an interest point in an image having a plurality of pixels suitable for working at different scales and/or rotations, the method comprising:
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filtering the image using at least one digital filter, and selecting an interest point based on determining a measure resulting from application of the at least one digital filter, the measure being a non-linear combination of the outputs of the at least one digital filter, the application of the at least one digital filter using integral images. - View Dependent Claims (24)
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Specification