COMPUTER VISION, 6RAPmCS, AND iMAGE PROCESSING 36, 133-135 (1986)

Abstracts of Papers Accepted for Publication

PAPERS

Analyzing Oriented Patterns. MICHAEL KASS AND ANDREW WITKIN. Schlumberger Palo Alto Re- search, 3340 HiUview Avenue, Palo Alto, California 94304. Received September 3, 1985; accepted November 4, 1985.

Oriented patterns, such as those produced by propagation, accretion, or deformation, are common in nature and therefore an important class for visual analysis. Our approach to understanding such patterns is to decompose them into two parts: the flow field, describing the direction of anisotropy; and the residual pattern obtained by describing the image in a coordinate system built from the flow field. We develop a method for the local estimation of anisotropy and a method for combining the estimates to construct a flow coordinate system. Several examples of the use of these methods are presented. These include the use of the flow coordinates to provide preferred directions for edge detection, detection of anomalies, fitting simple models to the straightened pattern, and detecting singularities in the flow field.

Fast Binary-Image Boundary Extraction. W. H. H. J. LUNSC~R. Develcon Electronics, Saskatoon, Saskatchewan, Canada S7K 5C7. M. P. B~DDO~S. Department of Electrical Engineering, The University of British Columbia, Vancouver, British Columbia, Canada V6T lW5. Received November 11, 1984; accepted March 14, 1986.

A scheme for obtaining boundaries of binary images is presented. It was inspired by Zahn. In 1969 he showed how to obtain outlines from a raster scanned binary image using a 3 • 2 pixel operator. The present proposal uses a slightly larger operator; it will produce complete descriptions of all closed borders (borders which encounter the outer edges of image space are not included): A nice feature is that only two of the most recently scanned lines of picture must be stored at any one time. Boundaries are continuously calculated during the scan; lookup tables and lists log and link the border points. It is important to signal when a closed contour has been detected. A very fast new, but not infallible, technique based on Euler numbers is proposed. Indication of closure is not guaranteed but it can be used to trigger slow-acting closure verification resulting in reduced processing overhead. Implementation design topics are illustrated in a number of simulations involving segmentation of 50 random-noise images. The results show that the real-time constraint can be satisfied with current technology when the natural parallelism within the system is exploited.

Data Dependent Filters for Edge Enhancement of Landsat Images. KNUT CONRADSEN AND GERT NILSSON. IMSOR, The Technical University of Denmark, DK-2800 Lyngby, Denmark. Received May 22, 1985; revised March 10, 1986.

In the paper some 2D filters are presented that are very efficient in edge enhancement of Landsat imagery. The filtered images are obtained as differences between the original images and some minimum mean-squared error predictions based on suitably chosen "predictor sets." The filters are compared to other high-pass filters such as the Laplacian and Gaussian filters, and they compare very favorably.

Derivation of Optical Flow Using a Spatiotemporal-Frequency Approach. LOWELL JACOBSON AND HARRY WECHSI~R. Department of Electrical Engineering, University of Minnesota, Minneapolis, Minnesota 55455. Received May 7, 1986.

We advance in this paper the spatiotemporal-frequency (STF) approach for computing the optical flow of a time-varying image. STF flow derivation provides an attractive alternative to earlier approaches

0734-189X/86 $3.00 Copyright �9 1986 by Academic Press, Inc.

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