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Journal ArticleDOI

The design and use of steerable filters

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TLDR
The authors present an efficient architecture to synthesize filters of arbitrary orientations from linear combinations of basis filters, allowing one to adaptively steer a filter to any orientation, and to determine analytically the filter output as a function of orientation.
Abstract
The authors present an efficient architecture to synthesize filters of arbitrary orientations from linear combinations of basis filters, allowing one to adaptively steer a filter to any orientation, and to determine analytically the filter output as a function of orientation. Steerable filters may be designed in quadrature pairs to allow adaptive control over phase as well as orientation. The authors show how to design and steer the filters and present examples of their use in the analysis of orientation and phase, angularly adaptive filtering, edge detection, and shape from shading. One can also build a self-similar steerable pyramid representation. The same concepts can be generalized to the design of 3-D steerable filters. >

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Citations
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Journal ArticleDOI

A modified k-means algorithm for circular invariant clustering

TL;DR: A distance measure and a k-means-based algorithm to cluster vectors containing directional information, such as F/sub d/, in a circular-shift invariant manner, which demonstrates the superior performance of the proposed algorithm for clustering directional vectors F/ sub d/, compared to the alternative approach.
Journal ArticleDOI

Wavelets in Temporal and Spatial Processing of Biomedical Images

TL;DR: Key concepts in the processing of medical images with wavelet transforms and multiscale analysis are reviewed, including time-frequency tiling, overcomplete representations, higher dimensional bases, symmetry, boundary effects, translational invariance, orientation selectivity, and best-basis selection.
Proceedings ArticleDOI

Automatic Detection of Intestinal Juices in Wireless Capsule Video Endoscopy

TL;DR: A method for the rejection of the parts of the video resulting not valid for analysis by means of automatic detection of intestinal juices is proposed, which achieves a significant reduction in visualization time, with no relevant loss of valid frames.
Proceedings ArticleDOI

A simple generic attack on text captchas

TL;DR: This paper reports a simple, low-cost but powerful attack that effectively breaks a wide range of text Captchas with distinct design features, including those deployed by Google, Microsoft, Yahoo!, Amazon and other Internet giants.
Journal ArticleDOI

Network model of top-down influences on local gain and contextual interactions in visual cortex

TL;DR: A network model based on an interaction between recurrent inputs to V1 and intrinsic connections within V1, which accounts for task-dependent changes in the properties of V1 neurons, and shows how a simple form of top-down modulation of the effective connectivity of intrinsic cortical connections among biophysically realistic neurons can account for some of the response changes seen in perceptual learning and task switching.
References
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Journal ArticleDOI

A Computational Approach to Edge Detection

TL;DR: There is a natural uncertainty principle between detection and localization performance, which are the two main goals, and with this principle a single operator shape is derived which is optimal at any scale.
Journal ArticleDOI

A theory for multiresolution signal decomposition: the wavelet representation

TL;DR: In this paper, it is shown that the difference of information between the approximation of a signal at the resolutions 2/sup j+1/ and 2 /sup j/ (where j is an integer) can be extracted by decomposing this signal on a wavelet orthonormal basis of L/sup 2/(R/sup n/), the vector space of measurable, square-integrable n-dimensional functions.
Book

Methods of Mathematical Physics

TL;DR: In this paper, the authors present an algebraic extension of LINEAR TRANSFORMATIONS and QUADRATIC FORMS, and apply it to EIGEN-VARIATIONS.