Measuring the Significance of Image Relations
PERCEPTUAL ORGANIZATION can be viewed as a process that assigns a degree of significance to each potential grouping of image features. Our goal in this chapter will be to take a unified view of the many grouping phenomena by examining the underlying principles for measuring the significance of each grouping. As was described in Chapter 1, perceptual groupings are useful to the extent that they are unlikely to have arisen by accident of viewpoint or position, and therefore are likely to reflect meaningful structure of the scene. Our basic argument will be that certain image relations are carriers of statistical information indicating that they are non-accidental in origin, and that this degree of non-accidentalness forms the basis for assigning degrees of significance. Note that there are an infinite number of different types of relations that could be considered (e.g., “all pairs of straight line segments at N degrees relative orientation,” for any given N), and a combinatorial number of sets of elements to consider in any given image. Only a small subset of these possible relations are likely to be of any significance or are worth the effort required for detection.
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