An Image Segmentation Technique based on Edge-preserving smoothing filter and Anisotropic Diffusion Tuan DANG Email: dang.t@lemel.fr http://www.multimania.com/dangt Abstract: An efficient and simple segmentation algorithm is presented which is based on a good edge-preserving smoothing filter and a fast anisotropic diffusion technique. A number of examples are shown to demonstrate the capabilities of this algorithm. Key Words: Image segmentation, Contrast enhancement, Smoothing filters, anisotropic diffusion. 1. Introduction A fundamental step in most of vision systems is to generate a compact description of an image, which is easier to be interpreted than a set of pixels. In order to achieve this, a wide variety of methods have been proposed for image segmentation. Among these techniques, one could find out mainly two approaches: 1) contours segmentation (edge detection plus contours tracing) and 2) region segmentation (grouping of connected pixels into regions of uniform properties). In this paper we propose a fast and simple region segmentation algorithm based on an edge- preserving smoothing filter, the symmetric nearest neighbor mean [1] and a fast anisotropic diffusion [2] which is followed by a region growing technique and a merging scheme. The details of the algorithm are discussed in Section 2. A number of examples demonstrating the capabilities of this technique are shown in Section 3. 2. Segmentation based on edge- preserving smoothing filter and anisotropic diffusion 2.1 Edge-preserving smoothing filters Edge-preserving smoothing filters designate a class of edge-preserving noise- cleaning filters. Many comparative studies of various edge-preserving noise smoothing techniques [1] [3] indicate that the Symmetric Nearest Neighbor (SNN) filters give the best results in both smoothing and preserving edges. So the SNN filters have often been used as an image enhancement technique. Westman et al [4] have used a SNN filter to preprocess color images before segmenting them. The principle of the SNN filters is described below. The SNN filters make use of both the spatial and gray value information in the neighborhood of a pixel to be processed. In a square window, half the number of pixels is selected by choosing one pixel nearest in gray value to the center pixel from each pair of pixels located symmetrically opposite the center. Only the selected pixels are used to compute a new value for the center pixel. 2.2 Anisotropic diffusion Anisotropic diffusion is a technique proposed by Perona and Malik [6] to selectively enhance contrast by using a modified heat diffusion equation. The technique is basically a discontinuity- preserving smoothing approach and closely related to the adaptive smoothing proposed