Detection of features in images
First Claim
1. A method of detecting features-of interest in an image, comprising:
- using a processor to perform steps of;
processing the image to make an intensity independent representation of an image intensity profile;
comparing the intensity independent representation with an intensity independent shape model for predefined features of interest by;
convolving the intensity independent representation with a quadrature filter to derive the phase and amplitude of a pair of odd and even components of the profile in the spatial or spatio temporal frequency domains;
deriving from a difference between the components a measure of one of the feature symmetry or asymmetry along the profile,deriving from the components a measure of the local amplitude along the profile; and
defining areas of the image satisfying a predefined constraint on the value of said one of the feature symmetry or asymmetry as satisfying the shape model and thus belonging to an image feature; and
storing for the profile a label comprising said measures.
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Accused Products
Abstract
An image processing technique which identifies pixels in images which are associated with features having a selected shape, such as but not exclusively step edge, roof, ridge or valley. The shape of the intensity profile in the image is compared in an intensity independent way with a shape model to select those pixels which satisfy the shape model and are thus associated with the feature of interest. This comparison is achieved by examining the phase and amplitude of a spectral decomposition of parts of the image profile in the spatial or spatio temporal frequency domain. This decomposition can be achieved using quadrature wavelet pairs such as log-Gabor wavelets. The difference between the odd and even components, known as the feature asymmetry, gives an indication of the shape of the feature. The analysis may be extended to the time domain by looking at the shape of the image profile across a time sequence of images, which gives an indication of the velocity of a moving feature. Pixels identified as belonging to a feature of the right shape are labelled with the value of feature asymmetry, the local amplitude, feature orientation and feature velocity, and this information can be used to improve the tracking of detected features through a sequence of images.
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Citations
23 Claims
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1. A method of detecting features-of interest in an image, comprising:
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using a processor to perform steps of; processing the image to make an intensity independent representation of an image intensity profile; comparing the intensity independent representation with an intensity independent shape model for predefined features of interest by; convolving the intensity independent representation with a quadrature filter to derive the phase and amplitude of a pair of odd and even components of the profile in the spatial or spatio temporal frequency domains; deriving from a difference between the components a measure of one of the feature symmetry or asymmetry along the profile, deriving from the components a measure of the local amplitude along the profile; and defining areas of the image satisfying a predefined constraint on the value of said one of the feature symmetry or asymmetry as satisfying the shape model and thus belonging to an image feature; and storing for the profile a label comprising said measures. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 23)
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22. A computer program stored on a computer readable medium and comprising program code which is executable by a processor to perform a method of detecting features-of-interest in an image, the method comprising:
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processing the image to make an intensity independent representation of an image intensity profile; comparing the intensity independent representation with an intensity independent shape model for predefined features of interest by; convolving the intensity independent representation with a quadrature filter to derive the phase and amplitude of a pair of odd and even components of the profile in the spatial or spatio temporal frequency domains; deriving from a difference between the components a measure of one of the feature symmetry or asymmetry along the profile, deriving from the components a measure of the local amplitude along the profile; and defining areas of the image satisfying a predefined constraint on the value of said one of the feature symmetry or asymmetry as satisfying the shape model and thus belonging to an image feature; and storing for the profile a label comprising said measures.
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Specification