Perceptual Grouping from Gabor Filter Responses

Perceptual organisation can be defined as the ability to impose structural organisation on sensory data, so as to group sensory primitives arising from a common underlying cause. Our organisational philosophy is hierarchical, with complex organisations being formed from simpler ones. In this paper, directional features extracted from Gabor responses are used as the primitives for perceptual grouping. In previous work, we extracted Gabor features in 8 directions and then applied two SOMs, thus classifying each pixel in the image within a 8x10 neuronmap, each corner of which represents one of four main directions, (horizontal, vertical, left diagonal and right diagonal). In the present work we group pixels with similar directional features, thereby detecting salient structures within an image. These detected-structures will be used as tokens from which to create the next level of abstraction in the hierarchy of the system. This approach is an alternative to the use of sets of edges as primary features: the directional features that Gabor filters provide are a potentially richer source of information. Preliminary results obtained from application to forward-looking infrared (FLIR) images are very promising. At present only four main directions are utilised, i.e. vertical, horizontal, right diagonal and left diagonal: the technique may be readily extended to the eight utilised in previous work. The next stage will be to group the tokens by the application of additional Gestalt-laws in order to detect objects.