1 Digital Image (i) What determines where the image of a 3D point appears on the 2D image? (ii) What determines how bright that image point is? Reflectance, radiometry geometry

2 Topics on feature detection: points of interest, (or corners  ) 1D features --- edge detection --- Canny-like 2D features --- points of interest

3 Image filtering or smoothing: Most often:

4 First derivative: The point having ||(gx,gy)||>threshold is a candidate, and becomes an edge point if it is a local maximum in the gradient direction gy/gx. Sobel if f is taken to be Gaussian, …, Canny-like detector

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6 Auto-correlation function for each pt p: Up to first order: The point having two strong eigenvalues is a candidate, and becomes a point of interest if it is a local maximum. Harris&Stephen, Moravec-Lucas-Kanade Intepreted as an ellipse

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