Issue No. 05 - May (1986 vol. 8)
Andres Huertas , Intelligent Systems Group, Department of Electrical Engineering, University of Southern California, Los Angeles, CA, 90089.
Gerard Medioni , Intelligent Systems Group, Department of Electrical Engineering, University of Southern California, Los Angeles, CA, 90089.
We present a system that takes a gray level image as input, locates edges with subpixel accuracy, and links them into lines. Edges are detected by finding zero-crossings in the convolution of the image with Laplacian-of-Gaussian (LoG) masks. The implementation differs markedly from M.I.T.'s as we decompose our masks exactly into a sum of two separable filters instead of the usual approximation by a difference of two Gaussians (DOG). Subpixel accuracy is obtained through the use of the facet model . We also note that the zero-crossings obtained from the full resolution image using a space constant ¿ for the Gaussian, and those obtained from the 1/n resolution image with 1/n pixel accuracy and a space constant of ¿/n for the Gaussian, are very similar, but the processing times are very different. Finally, these edges are grouped into lines using the technique described in .
G. Medioni and A. Huertas, "Detection of Intensity Changes with Subpixel Accuracy Using Laplacian-Gaussian Masks," in IEEE Transactions on Pattern Analysis & Machine Intelligence, vol. 8, no. , pp. 651-664, 1986.