Edge Detection

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Edges correspond to regions of rapid intensity change. Common operators:

• Sobel / Prewitt: first-order derivative filters for gradient magnitude and direction.

• Laplacian of Gaussian (LoG): second-order operator; detects zero-crossings.

• Canny edge detector: multi-stage pipeline (Gaussian smoothing → gradient → non-maximum suppression → hysteresis thresholding); widely regarded as optimal for general use.

See also

• Spatial Filtering — the smoothing filters that usually precede edge detection

• Thresholding and Binarization — turning an edge/gradient image into a binary mask

• Edge Detection and Gradient Images — these operators applied as a concrete preprocessing step

• Digital Image Processing Basics — every other basics topic