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Image gradients, Sobel, and Canny

Source: interviewbeginner

WHAT IT TESTS: edge-detection foundations. OUTLINE: the gradient measures local intensity change in x and y; Sobel approximates it via convolution kernels; Canny uses gradient magnitude and direction plus non-max suppression and hysteresis.

WHAT IT TESTS: whether you connect derivatives to edges. ANSWER OUTLINE: an image gradient is the vector of partial derivatives of intensity in x and y; its magnitude marks how sharply brightness changes and its direction points across the edge. Sobel approximates these derivatives with small convolution kernels that also smooth. Canny builds on the gradient: smooth, compute gradient magnitude and direction, apply non-maximum suppression to thin edges, then double-threshold with hysteresis to link them.

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Image gradients, Sobel, and Canny · Tezvyn