Edges represent the most fundamental features in images and serve as the first step in image segmentation. Classical edge detection methods—such as Roberts, Sobel, Prewitt, Kirsch, and Laplace—generally operate by constructing small neighborhood operators to compute first or second-order derivatives, identifying gradient maxima or zero-crossings of the second derivative, and finally applying a suitable threshold to extract boundaries. These gradient-based methods, however, are noise-sensitive and computationally intensive. In contrast, the SUSAN (Smallest Univalue Segment Assimilating Nucleus) algorithm relies solely on grayscale comparisons of surrounding pixels without any gradient calculations, making it highly robust to noise and computationally efficient. SUSAN has been effectively applied in edge detection for various types of images.
MATLAB
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