Composite phase and phase-based Gabor element aggregation

This paper describes how the phase, obtained by Gabor filtering an image, can be used to aggregate related Gabor elements (simple features identified by peaks in the Gabor magnitude). This phase-based feature grouping simplifies the perennial problem of target/background segmentation because we need to only determine if the aggregate feature is target or background, rather than determine the status of each feature independently. Since the phase from a single quadrature Gabor output cannot tolerate large changes in orientation, a new local measure, referred to as the composite phase, has been developed. It is a combination of the filter responses from multiple orientations which allows the phase to follow contours with large changes in orientation. A constant composite phase contour is used to connect related Gabor elements that would otherwise appear separated within the magnitude response.