Q9Digital Image Processing

Edge detection is an image processing technique used to identify points in a digital image where the image brightness changes sharply or has discontinuities, typically marking the boundary between two distinct regions. It is implemented using first-order derivative (gradient) operators such as Sobel, Prewitt, and Roberts, which respond strongly to edges but are sensitive to noise, or second-order derivative operators such as the Laplacian, which locate edges at zero crossings. Because raw derivatives amplify noise, edge detectors are commonly preceded by smoothing, as in the Canny detector, which combines Gaussian smoothing, gradient computation, non-maximum suppression, and hysteresis thresholding to produce thin, well-localized edges.