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 being divided into sub-regions, each sub-region comprising a set of pixels;
inspecting contrasts at pixels of the set of pixels in the sub-regions in at least two directions having a fixed relation to the orientation using at least one first digital filter to thereby generate first scalar contrast measures for each direction independently, each first scalar contrast measure being a component of an intensity gradient represented by the change of contrast or image intensity along each direction at each pixel of the set of pixels; 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.
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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 data structures associating such descriptors with an original copy of the image or an image derived therefrom, e.g. a thumbnail image.
56 Citations
20 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 being divided into sub-regions, each sub-region comprising a set of pixels; inspecting contrasts at pixels of the set of pixels in the sub-regions in at least two directions having a fixed relation to the orientation using at least one first digital filter to thereby generate first scalar contrast measures for each direction independently, each first scalar contrast measure being a component of an intensity gradient represented by the change of contrast or image intensity along each direction at each pixel of the set of pixels; 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 (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification